Recent update to kernel 5.4.0-94 gave black screen for login

[phonic-otg]

Hello, this will be a clumsy post. As an end user, I am clumsy with commands, so apologies in advance.

My OS is on a micro SD card with a full install (named phonic-otg) and has been working like a charm on my laptop until the botched update (I also have a live USB with persistence for troubleshooting).
With the last update from Discover for the kernel and images etc associated with the title kernel (5.4.0-94) there was some sort of hiccup. After it downloaded them it started to install and got halfway through installing the first one then just hanged for about an hour, I rebooted and used discover again with the same result. I decided to reboot and use Konsole to do the update/upgrade, all seemed well until the next morning.

I got a blank screen after the startup splash screen and no login. Rebooted to use the kernel recovery in grub, a few times trying fsck and dpkg also with no luck so started networking in recovery and dropped into the root cli and started a GUI with startx to use Konsole to try fsck which said I need to unmount first. So I used my live USB to do fsck on the USB with the issue (fsck -tf /dev/sdb5) restarted and then tried to use the phonic-otg USB with success, it gave me my login, and I was able to use things as normal. I thought the issue was solved but no, the same issue returned the next morning (today) I tried to startx from the TTY, but it didn't work. One of the dpkg errors said E Sub-process /usr/bin/dpkg returned an error 1. So I used my phone to search the issue and got many commands to try. I took photos of some and tried the script command to save the command's output from the TTY session and root recovery with weird results that show the command but the output recorded is gobbledegook. The main issue seems to be with a dpkg error.

I have attached the output files and photo screenshots, also I can't attach any log files, so I saved them as a txt file.
EDIT: not all attachment posted, so I will put them in a reply post.

[phonic-otg]

I am having a heck of a time getting to upload attachment photos (under 2mb).
So it is just txt files of logs and Konsole saves.

[claydoh]

Don't rule out the sdcard nearing the end of its life, so make sure you have backups.

Some of your log output is unreadable gibberish, not sure why, but it reinforces my thoughts on the sdcard going south.

Standard package install issues would be to run:
sudo dpkg --configure -a
and
sudo apt -fix-missing install


From the tail end, I see that there are issues with ubuntu-advantage-tools, which you might just uninstall for now, if the above doesn't fix it. it is not a vital.

As for image upload, I am not sure if there is a limit on the number of files per post, but it is easiest to just drag the file(s) from Dolphin, Gwenview, or the clipboard. to the post window, and you will see a drop target appear. The new forum upgrade software seems to be able to handle and resize larger images, but mobile may behave differently
Having said that, not sure yet what things look like from mobile for uploading.

[phonic-otg]

Thanks for the response. The SD card is not that old, about a year and is rarely used as I only use it for travelling trips with my laptop.

Standard package install issues would be to run:
sudo dpkg --configure -a
and
sudo apt -fix-missing install

I have done those early on. The attached photos show it.
I did them again today, here is the result.

root@phonic-otg:~# sudo dpkg --configure -a
Setting up ubuntu-advantage-tools (27.5~20.04.1) ...
Traceback (most recent call last):
File "/usr/bin/py3compile", line 34, in <module>
from debpython.version import SUPPORTED, debsorted, vrepr, \
ModuleNotFoundError: No module named 'debpython.version'
dpkg: error processing package ubuntu-advantage-tools (--configure):
installed ubuntu-advantage-tools package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:
ubuntu-advantage-tools
root@phonic-otg:~# sudo apt -fix-missing install
E: Command line option 'i' [from -fix-missing] is not understood in combination with the other options.
root@phonic-otg:~#

Can't seem to get rid of ubuntu-advantage-tools (I tried to script command the output, but it came out with gibberish) below is a copy and paste of the Konsole session.

root@phonic-otg:~# script /home/phonic/retryfix.txt
Script started, file is /home/phonic/retryfix.txt
root@phonic-otg:~# sudo apt-get remove --purge ubuntu-advantage-tools
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be REMOVED:
ubuntu-advantage-tools*
0 to upgrade, 0 to newly install, 1 to remove and 2 not to upgrade.
1 not fully installed or removed.
After this operation, 3,259 kB disk space will be freed.
Do you want to continue? [Y/n] y
(Reading database ... 345546 files and directories currently installed.)
Removing ubuntu-advantage-tools (27.5~20.04.1) ...
Traceback (most recent call last):
File "/usr/bin/py3clean", line 32, in <module>
from debpython import files as dpf
ImportError: cannot import name 'files' from 'debpython' (unknown location)
dpkg: error processing package ubuntu-advantage-tools (--remove):
installed ubuntu-advantage-tools package pre-removal script subprocess returned error exit status 1
dpkg: too many errors, stopping
Traceback (most recent call last):
File "/usr/bin/py3compile", line 34, in <module>
from debpython.version import SUPPORTED, debsorted, vrepr, \
ModuleNotFoundError: No module named 'debpython.version'
dpkg: error while cleaning up:
installed ubuntu-advantage-tools package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:
ubuntu-advantage-tools
Processing was halted because there were too many errors.
E: Sub-process /usr/bin/dpkg returned an error code (1)

If I can't fix this mess, is there a way to just reinstall the updates, overwriting the corrupted ones?

[claydoh]

whooops , it should be '--fix-missing" , I missed the second dash.
But that wont magically fix things

The Ubuntu-advantage-tools package might need to have some scalpel work done.
We can try removing all the install/removal scripts for this:

sudo rm /var/lib/dpkg/info/ubuntu-advantage-tools.*
sudo apt clean
Then try to reinstall:

sudo apt update
sudo apt install --reinstall ubuntu-advantage-tools


As to the age of the sdcard, it is still worth keeping an eye on, from my own experience using these on various systems specifically to run an OS in recent years. Even good quality Samsungs would die in well less than a year. They are just not designed for the constant simultaneous reads/writes an OS needs, particularly a full-featured desktop distro. Just something to keep in mind.

[phonic-otg]

I could not do this from the tty as there is no networking, only in a recovery root gui can I get networking.
Ok, I tried to remove u-a-t it came back saying it's not there. Then tried to reinstall and it came back with an internal error.

root@phonic-otg:~# sudo rm /var/lib/dpkg/info/ubuntu-advantage-tools
rm: cannot remove '/var/lib/dpkg/info/ubuntu-advantage-tools': No such file or directory
root@phonic-otg:~# sudo apt update
Hit:1 http://ppa.launchpad.net/kdenlive/kd...-stable/ubuntu focal InRelease
Hit:2 http://au.archive.ubuntu.com/ubuntu focal InRelease
Hit:3 http://security.ubuntu.com/ubuntu focal-security InRelease
Hit:4 http://au.archive.ubuntu.com/ubuntu focal-updates InRelease
Hit:5 http://au.archive.ubuntu.com/ubuntu focal-backports InRelease
Hit:6 http://ppa.launchpad.net/ubuntuhandbook1/gimp/ubuntu focal InRelease
Reading package lists... Done
Building dependency tree
Reading state information... Done
All packages are up to date.
root@phonic-otg:~# sudo apt install --reinstall ubuntu-advantage-tools
Reading package lists... Done
Building dependency tree
Reading state information... Done
0 to upgrade, 0 to newly install, 1 to reinstall, 0 to remove and 0 not to upgrade.
1 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
E: Internal Error, No file name for ubuntu-advantage-tools:amd64

Do I need to add a PPA for it?

I was wondering If I remove the recent files for 5.4.0-94 with

sudo apt-get purge linux-image5.4.0-94-generic

will it remove the vmlinuz, System.map, initrd.img, config, modules and headers too?

[claydoh]

You don't need ubuntu-advantage-tools unless you are a paying customer.

sudo rm /var/lib/dpkg/info/ubuntu-advantage-tools.*
You missed the '*' at the end.

But if you get no errors running
sudo dpkg --configure -a
and
sudo apt --fix-missing install
you don't have to worry about it.

You can test apt using the --dry-run option

apt purge --dry-run linux-image-5.4.0-94-generic

Done
The following package was automatically installed and is no longer required:
linux-modules-5.4.0-94-generic
Use 'apt autoremove' to remove it.
The following packages will be REMOVED:
linux-image-5.4.0-94-generic* linux-image-generic* linux-modules-extra-5.4.0-94-generic*

But linux-image-generic is kind of important as it is the main meta-package. You won't get any 5.4 kernel updates any longer unless you manually install them, if this is removed. Not at all sure if holding the 'good' kernel works the same as regular packages, since they keep a few around. I am sure someon here knows more about that than I do.

In any case, the initrd will be regenerated as it is whenever a kernel is added/removed, and files relevant to -94 will also be removed.

[phonic-otg]

Thanks, looks like I don't have ubuntu-advantage-tools to worry about getting in the way as there were no errors for any of the commands.

root@phonic-otg:~# sudo rm /var/lib/dpkg/info/ubuntu-advantage-tools.*
root@phonic-otg:~# sudo dpkg --configure -a
Setting up ubuntu-advantage-tools (27.5~20.04.1) ...
root@phonic-otg:~# sudo apt --fix-missing install
Reading package lists... Done
Building dependency tree
Reading state information... Done
0 to upgrade, 0 to newly install, 0 to remove and 0 not to upgrade.

I take it that --dry-run is testing what will happen if I purge the kernel. I am wondering if there is a way to overwrite the kernel and its dependencies with fresh ones before purging. If I do decide to purge, is there a way to exclude linux-image-generic?

--dry-run output

root@phonic-otg:~# apt purge --dry-run linux-image-5.4.0-94-generic
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
amd64-microcode intel-microcode iucode-tool linux-headers-generic thermald
Use 'apt autoremove' to remove them.
The following additional packages will be installed:
linux-image-unsigned-5.4.0-94-generic
Suggested packages:
fdutils linux-doc | linux-source-5.4.0 linux-tools
The following packages will be REMOVED:
linux-generic* linux-image-5.4.0-94-generic* linux-image-generic*
linux-modules-extra-5.4.0-94-generic*
The following NEW packages will be installed:
linux-image-unsigned-5.4.0-94-generic
0 to upgrade, 1 to newly install, 4 to remove and 0 not to upgrade.
Purg linux-generic [5.4.0.94.98]
Purg linux-image-generic [5.4.0.94.98]
Purg linux-modules-extra-5.4.0-94-generic [5.4.0-94.106]
Purg linux-image-5.4.0-94-generic [5.4.0-94.106]
Inst linux-image-unsigned-5.4.0-94-generic (5.4.0-94.106 Ubuntu:20.04/focal-updates, Ubuntu:20.04/focal-
security [amd64])
Conf linux-image-unsigned-5.4.0-94-generic (5.4.0-94.106 Ubuntu:20.04/focal-updates, Ubuntu:20.04/focal-
security [amd64])

EDIT: I don't think it is the kernel that is my issue, as the fsck (from live USB) rectified the issue momentarily before it came back. I have tried every kernel, and they all go to a blank screen after the Kubuntu splash. After using the recovery kernel and startx, there was 2 FAIL messages, too quick for me to read but managed to get a photo. Could they be my issue?

[claydoh]

Use apt install --reinstall <package> to try to re-do, which should re-run the install of the package, including its setup scripts

I still think it is a possibly corrupt sdard at play here. At least potentially.

[phonic-otg]

Using the root GUI for 5.4.0-94, I did the reinstall, and updated grub. There is a dpkg warning about ubuntu-advantage-tools not being there.

root@phonic-otg:~# apt-get update
Hit:1 http://au.archive.ubuntu.com/ubuntu focal InRelease
Get:2 http://au.archive.ubuntu.com/ubuntu focal-updates InRelease [114 kB]
Get:3 http://au.archive.ubuntu.com/ubuntu focal-backports InRelease [108 kB]
Get:4 http://au.archive.ubuntu.com/ubuntu focal-updates/main amd64 DEP-11 Metadata [280 kB]
Get:5 http://au.archive.ubuntu.com/ubuntu focal-updates/universe amd64 DEP-11 Metadata [362 kB]
Get:6 http://security.ubuntu.com/ubuntu focal-security InRelease [114 kB]
Get:7 http://au.archive.ubuntu.com/ubuntu focal-updates/multiverse amd64 DEP-11 Metadata [944 B]
Get:8 http://au.archive.ubuntu.com/ubuntu focal-backports/main amd64 DEP-11 Metadata [8,000 B]
Get:9 http://au.archive.ubuntu.com/ubuntu focal-backports/universe amd64 DEP-11 Metadata [11.3 kB]
Hit:10 http://ppa.launchpad.net/kdenlive/kd...-stable/ubuntu focal InRelease
Hit:11 http://ppa.launchpad.net/ubuntuhandbook1/gimp/ubuntu focal InRelease
Get:12 http://security.ubuntu.com/ubuntu focal-security/main amd64 DEP-11 Metadata [38.2 kB]
Get:13 http://security.ubuntu.com/ubuntu focal-security/universe amd64 DEP-11 Metadata [66.2 kB]
Get:14 http://security.ubuntu.com/ubuntu focal-security/multiverse amd64 DEP-11 Metadata [2,464 B]
Fetched 1,105 kB in 4s (316 kB/s)
Reading package lists... Done
root@phonic-otg:~# apt install --reinstall linux-image-5.4.0-94-generic
Reading package lists... Done
Building dependency tree
Reading state information... Done
0 to upgrade, 0 to newly install, 1 to reinstall, 0 to remove and 0 not to upgrade.
Need to get 10.5 MB of archives.
After this operation, 0 B of additional disk space will be used.
Get:1 http://au.archive.ubuntu.com/ubuntu focal-updates/main amd64 linux-image-5.4.0-94-generic amd64 5.
4.0-94.106 [10.5 MB]
Fetched 10.5 MB in 6s (1,755 kB/s)
dpkg:warning: files list file for package 'ubuntu-advantage-tools' missing; assuming package has no fil
es currently installed
(Reading database ... 345559 files and directories currently installed.)
Preparing to unpack .../linux-image-5.4.0-94-generic_5.4.0-94.106_amd64.deb ...
Unpacking linux-image-5.4.0-94-generic (5.4.0-94.106) over (5.4.0-94.106) ...
Setting up linux-image-5.4.0-94-generic (5.4.0-94.106) ...
Processing triggers for linux-image-5.4.0-94-generic (5.4.0-94.106) ...
/etc/kernel/postinst.d/initramfs-tools:
update-initramfs: Generating /boot/initrd.img-5.4.0-94-generic
/etc/kernel/postinst.d/zz-update-grub:
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/init-select.cfg'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-5.4.0-94-generic
Found initrd image: /boot/initrd.img-5.4.0-94-generic
Found linux image: /boot/vmlinuz-5.4.0-92-generic
Found initrd image: /boot/initrd.img-5.4.0-92-generic
Found linux image: /boot/vmlinuz-5.4.0-91-generic
Found initrd image: /boot/initrd.img-5.4.0-91-generic
Found linux image: /boot/vmlinuz-5.4.0-90-generic
Found initrd image: /boot/initrd.img-5.4.0-90-generic
Found linux image: /boot/vmlinuz-5.4.0-89-generic
Found initrd image: /boot/initrd.img-5.4.0-89-generic
Found memtest86+ image: /boot/memtest86+.elf
Found memtest86+ image: /boot/memtest86+.bin
done
root@phonic-otg:~# update-grub
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/init-select.cfg'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-5.4.0-94-generic
Found initrd image: /boot/initrd.img-5.4.0-94-generic
Found linux image: /boot/vmlinuz-5.4.0-92-generic
Found initrd image: /boot/initrd.img-5.4.0-92-generic
Found linux image: /boot/vmlinuz-5.4.0-91-generic
Found initrd image: /boot/initrd.img-5.4.0-91-generic
Found linux image: /boot/vmlinuz-5.4.0-90-generic
Found initrd image: /boot/initrd.img-5.4.0-90-generic
Found linux image: /boot/vmlinuz-5.4.0-89-generic
Found initrd image: /boot/initrd.img-5.4.0-89-generic
Found memtest86+ image: /boot/memtest86+.elf
Found memtest86+ image: /boot/memtest86+.bin
done

Going to reboot and see if there is any success.

[phonic-otg]

Booting to login, went further with messaging and a hung cursor.
There are similar Fail errors photo in post 8 of this thread.
Could the firmware for AMD be corrupted?
I am managing to run the root GUI from the Micro-SD card, so I don't think the card is corrupted yet.

EDIT: Searching about the firmware-bug led me to some pages that offered some insight.
On this page near the end, they say

I've also noticed that the offending param seems to be ivrs_ioapic[5]=00:02.0. In fact, if I boot the system only with ivrs_ioapic[4]=00:14.0 the firmware bug message disappears and the desktop boots as expected.

On this page, they suggest editing the GRUB_CMDLINE_LINUX_DEFAULT with various amd_iommu dump and flushes.

Here are some outputs of error journals and my system info.

root@phonic-otg:~# dmesg --level=err
[ 0.133564] AMD-Vi: [Firmware Bug]: : IOAPIC[4] not in IVRS table
[ 0.133737] AMD-Vi: [Firmware Bug]: : IOAPIC[5] not in IVRS table
[ 0.133903] AMD-Vi: [Firmware Bug]: : No southbridge IOAPIC found
[ 0.134068] AMD-Vi: Disabling interrupt remapping
[ 1.078347] tpm_crb MSFT0101:00: can't request region for resource [mem 0xbf7a2000-0xbf7a5fff]
[ 1.531146] [drm:amdgpu_init [amdgpu]] *ERROR* VGACON disables amdgpu kernel modesetting.
[ 3.041332] AMD-Vi: Event logged [IO_PAGE_FAULT device=00:00.0 domain=0x0000 address=0xfff123c0 flags=0x0050]
[ 3.041602] AMD-Vi: Event logged [IO_PAGE_FAULT device=00:00.0 domain=0x0000 address=0xfff123e0 flags=0x0050]
[ 3.041856] AMD-Vi: Event logged [IO_PAGE_FAULT device=00:00.0 domain=0x0000 address=0xfff12400 flags=0x0050]
[ 3.051375] AMD-Vi: Event logged [IO_PAGE_FAULT device=00:00.0 domain=0x0000 address=0xfff143c0 flags=0x0050]
[ 3.051631] AMD-Vi: Event logged [IO_PAGE_FAULT device=00:00.0 domain=0x0000 address=0xfff143e0 flags=0x0050]
[ 3.051890] AMD-Vi: Event logged [IO_PAGE_FAULT device=00:00.0 domain=0x0000 address=0xfff14400 flags=0x0050]
[ 3.061401] AMD-Vi: Event logged [IO_PAGE_FAULT device=00:00.0 domain=0x0000 address=0xfff143c0 flags=0x0050]
[ 3.061666] AMD-Vi: Event logged [IO_PAGE_FAULT device=00:00.0 domain=0x0000 address=0xfff143e0 flags=0x0050]
[ 3.061907] AMD-Vi: Event logged [IO_PAGE_FAULT device=00:00.0 domain=0x0000 address=0xfff14400 flags=0x0050]
[ 3.587445] sd 1:0:0:0: [sda] No Caching mode page found
[ 3.587616] sd 1:0:0:0: [sda] Assuming drive cache: write through
[ 12.607468] [drm:amdgpu_init [amdgpu]] *ERROR* VGACON disables amdgpu kernel modesetting.
[ 586.528337] rtw_pci 0000:01:00.0: failed to send h2c command
[ 1119.917415] rtw_pci 0000:01:00.0: failed to send h2c command

root@phonic-otg:~# journalctl -xb
-- Logs begin at Sat 2021-10-02 14:59:48 AEST, end at Mon 2022-01-17 16:23:45 AEDT. --
Jan 17 15:54:36 phonic-otg kernel: Linux version 5.4.0-94-generic (buildd@lcy02-amd64-053) (gcc version 9.3.0 (>
Jan 17 15:54:36 phonic-otg kernel: Command line: BOOT_IMAGE=/boot/vmlinuz-5.4.0-94-generic root=UUID=e3021682-6>
Jan 17 15:54:36 phonic-otg kernel: KERNEL supported cpus:
Jan 17 15:54:36 phonic-otg kernel: Intel GenuineIntel
Jan 17 15:54:36 phonic-otg kernel: AMD AuthenticAMD
Jan 17 15:54:36 phonic-otg kernel: Hygon HygonGenuine
Jan 17 15:54:36 phonic-otg kernel: Centaur CentaurHauls
Jan 17 15:54:36 phonic-otg kernel: zhaoxin Shanghai
Jan 17 15:54:36 phonic-otg kernel: x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'
Jan 17 15:54:36 phonic-otg kernel: x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
Jan 17 15:54:36 phonic-otg kernel: x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
Jan 17 15:54:36 phonic-otg kernel: x86/fpu: xstate_offset[2]: 576, xstate_sizes[2]: 256
Jan 17 15:54:36 phonic-otg kernel: x86/fpu: Enabled xstate features 0x7, context size is 832 bytes, using 'comp>
Jan 17 15:54:36 phonic-otg kernel: BIOS-provided physical RAM map:
Jan 17 15:54:36 phonic-otg kernel: BIOS-e820: [mem 0x0000000000000000-0x000000000009f7ff] usable
Jan 17 15:54:36 phonic-otg kernel: BIOS-e820: [mem 0x000000000009f800-0x000000000009ffff] reserved
Jan 17 15:54:36 phonic-otg kernel: BIOS-e820: [mem 0x00000000000e0000-0x00000000000fffff] reserved
Jan 17 15:54:36 phonic-otg kernel: BIOS-e820: [mem 0x0000000000100000-0x0000000009bfffff] usable
Jan 17 15:54:36 phonic-otg kernel: BIOS-e820: [mem 0x0000000009c00000-0x0000000009dfffff] reserved
Jan 17 15:54:36 phonic-otg kernel: BIOS-e820: [mem 0x0000000009e00000-0x0000000009efffff] usable
Jan 17 15:54:36 phonic-otg kernel: BIOS-e820: [mem 0x0000000009f00000-0x0000000009f09fff] ACPI NVS
Jan 17 15:54:36 phonic-otg kernel: BIOS-e820: [mem 0x0000000009f0a000-0x00000000a35a9fff] usable
Jan 17 15:54:36 phonic-otg kernel: BIOS-e820: [mem 0x00000000a35aa000-0x00000000a3ea9fff] reserved
Jan 17 15:54:36 phonic-otg kernel: BIOS-e820: [mem 0x00000000a3eaa000-0x00000000b4ebefff] usable
Jan 17 15:54:36 phonic-otg kernel: BIOS-e820: [mem 0x00000000b4ebf000-0x00000000beebefff] reserved

root@phonic-otg:~# lspci
00:00.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Raven/Raven2 Root Complex
00:00.2 IOMMU: Advanced Micro Devices, Inc. [AMD] Raven/Raven2 IOMMU
00:01.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-1fh) PCIe Dummy Host Bridge
00:01.2 PCI bridge: Advanced Micro Devices, Inc. [AMD] Raven/Raven2 PCIe GPP Bridge [6:0]
00:01.7 PCI bridge: Advanced Micro Devices, Inc. [AMD] Raven/Raven2 PCIe GPP Bridge [6:0]
00:08.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-1fh) PCIe Dummy Host Bridge
00:08.1 PCI bridge: Advanced Micro Devices, Inc. [AMD] Raven/Raven2 Internal PCIe GPP Bridge 0 to Bus A
00:08.2 PCI bridge: Advanced Micro Devices, Inc. [AMD] Raven/Raven2 Internal PCIe GPP Bridge 0 to Bus B
00:14.0 SMBus: Advanced Micro Devices, Inc. [AMD] FCH SMBus Controller (rev 61)
00:14.3 ISA bridge: Advanced Micro Devices, Inc. [AMD] FCH LPC Bridge (rev 51)
00:18.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Raven/Raven2 Device 24: Function 0
00:18.1 Host bridge: Advanced Micro Devices, Inc. [AMD] Raven/Raven2 Device 24: Function 1
00:18.2 Host bridge: Advanced Micro Devices, Inc. [AMD] Raven/Raven2 Device 24: Function 2
00:18.3 Host bridge: Advanced Micro Devices, Inc. [AMD] Raven/Raven2 Device 24: Function 3
00:18.4 Host bridge: Advanced Micro Devices, Inc. [AMD] Raven/Raven2 Device 24: Function 4
00:18.5 Host bridge: Advanced Micro Devices, Inc. [AMD] Raven/Raven2 Device 24: Function 5
00:18.6 Host bridge: Advanced Micro Devices, Inc. [AMD] Raven/Raven2 Device 24: Function 6
00:18.7 Host bridge: Advanced Micro Devices, Inc. [AMD] Raven/Raven2 Device 24: Function 7
01:00.0 Network controller: Realtek Semiconductor Co., Ltd. RTL8822BE 802.11a/b/g/n/ac WiFi adapter
02:00.0 Non-Volatile memory controller: SK hynix BC501 NVMe Solid State Drive 512GB
03:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Raven Ridge [Radeon Vega Series / Rade
on Vega Mobile Series] (rev c4)
03:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Raven/Raven2/Fenghuang HDMI/DP Audio Controller
03:00.2 Encryption controller: Advanced Micro Devices, Inc. [AMD] Family 17h (Models 10h-1fh) Platform Security
Processor
03:00.3 USB controller: Advanced Micro Devices, Inc. [AMD] Raven USB 3.1
03:00.4 USB controller: Advanced Micro Devices, Inc. [AMD] Raven USB 3.1
03:00.6 Audio device: Advanced Micro Devices, Inc. [AMD] Family 17h (Models 10h-1fh) HD Audio Controller
03:00.7 Non-VGA unclassified device: Advanced Micro Devices, Inc. [AMD] Raven/Raven2/Renoir Non-Sensor Fusion Hu
b KMDF driver
04:00.0 SATA controller: Advanced Micro Devices, Inc. [AMD] FCH SATA Controller [AHCI mode] (rev 61)
root@phonic-otg:~# amd_iommu_dump=1
root@phonic-otg:~# journalctl -p err -b -1
-- Logs begin at Sat 2021-10-02 14:59:48 AEST, end at Mon 2022-01-17 16:11:16 AEDT. --
Jan 17 15:45:36 phonic-otg kernel: AMD-Vi: [Firmware Bug]: : IOAPIC[4] not in IVRS table
Jan 17 15:45:36 phonic-otg kernel: AMD-Vi: [Firmware Bug]: : IOAPIC[5] not in IVRS table
Jan 17 15:45:36 phonic-otg kernel: AMD-Vi: [Firmware Bug]: : No southbridge IOAPIC found
Jan 17 15:45:36 phonic-otg kernel: AMD-Vi: Disabling interrupt remapping
Jan 17 15:45:36 phonic-otg kernel: tpm_crb MSFT0101:00: can't request region for resource [mem 0xbf7a2000-0xbf7>
Jan 17 15:45:36 phonic-otg kernel: AMD-Vi: Event logged [IO_PAGE_FAULT device=00:00.0 domain=0x0000 address=0xf>
Jan 17 15:45:36 phonic-otg kernel: AMD-Vi: Event logged [IO_PAGE_FAULT device=00:00.0 domain=0x0000 address=0xf>
Jan 17 15:45:36 phonic-otg kernel: AMD-Vi: Event logged [IO_PAGE_FAULT device=00:00.0 domain=0x0000 address=0xf>
Jan 17 15:45:36 phonic-otg kernel: AMD-Vi: Event logged [IO_PAGE_FAULT device=00:00.0 domain=0x0000 address=0xf>
Jan 17 15:45:36 phonic-otg kernel: AMD-Vi: Event logged [IO_PAGE_FAULT device=00:00.0 domain=0x0000 address=0xf>
Jan 17 15:45:36 phonic-otg kernel: AMD-Vi: Event logged [IO_PAGE_FAULT device=00:00.0 domain=0x0000 address=0xf>
Jan 17 15:45:36 phonic-otg kernel: AMD-Vi: Event logged [IO_PAGE_FAULT device=00:00.0 domain=0x0000 address=0xf>
Jan 17 15:45:36 phonic-otg kernel: AMD-Vi: Event logged [IO_PAGE_FAULT device=00:00.0 domain=0x0000 address=0xf>
Jan 17 15:45:36 phonic-otg kernel: AMD-Vi: Event logged [IO_PAGE_FAULT device=00:00.0 domain=0x0000 address=0xf>
Jan 17 15:45:36 phonic-otg kernel: sd 1:0:0:0: [sda] No Caching mode page found
Jan 17 15:45:36 phonic-otg kernel: sd 1:0:0:0: [sda] Assuming drive cache: write through
Jan 17 15:46:02 phonic-otg sddm[805]: Failed to read display number from pipe
Jan 17 15:46:02 phonic-otg sddm[805]: Display server failed to start. Exiting
Jan 17 15:46:04 phonic-otg sddm[2544]: Failed to read display number from pipe
Jan 17 15:46:04 phonic-otg sddm[2544]: Display server failed to start. Exiting
Jan 17 15:46:06 phonic-otg sddm[2587]: Failed to read display number from pipe
Jan 17 15:46:06 phonic-otg sddm[2587]: Display server failed to start. Exiting
Jan 17 15:46:08 phonic-otg sddm[2629]: Failed to read display number from pipe
Jan 17 15:46:08 phonic-otg sddm[2629]: Display server failed to start. Exiting
Jan 17 15:46:09 phonic-otg sddm[2671]: Failed to read display number from pipe
Jan 17 15:46:09 phonic-otg sddm[2671]: Display server failed to start. Exiting

[phonic-otg]

(All this is done in root recovery for 5.4.0-94)

So, I followed one (well 2) of the suggestions from the second link in post 11, The first was

sudo sed -i sed 's/GRUB_CMDLINE_LINUX_DEFAULT=\".*[^"]/& amd_iommu_dump=1/g' /etc/default/grub

and no error came from using the command.

The second was altering /etc/default/grub with GRUB_CMDLINE_LINUX_DEFAULT="quiet splash ivrs_ioapic[4]=00:14.0 ivrs_ioapic[5]=00:00.1" after which I did update-grub to which I got a syntax error message, so I restored the grub file by deleting the new entry I put in.
As I was about to reboot, I saw Discover had an update that was new Linux kernels, wary of my last discover experience I did the upgrade from Konsole which said three were held back.
After rebooting and some time as it is loading from a USB port I got success and my regular login was waiting for me. Loging in and checking info centre, it still showed 5.4.0-94 as the operating kernel, as did uname -r.
So then I decided to do the Discover update after it finished I checked with

dpkg --list | grep linux-image

and it gave

rc linux-image-5.4.0-26-generic 5.4.0-26.30 amd64 Signed kernel image generic
rc linux-image-5.4.0-88-generic 5.4.0-88.99 amd64 Signed kernel image generic
ii linux-image-5.4.0-89-generic 5.4.0-89.100 amd64 Signed kernel image generic
ii linux-image-5.4.0-90-generic 5.4.0-90.101 amd64 Signed kernel image generic
ii linux-image-5.4.0-91-generic 5.4.0-91.102 amd64 Signed kernel image generic
ii linux-image-5.4.0-92-generic 5.4.0-92.103 amd64 Signed kernel image generic
ii linux-image-5.4.0-94-generic 5.4.0-94.106 amd64 Signed kernel image generic
ii linux-image-5.4.0-96-generic 5.4.0-96.109 amd64 Signed kernel image generic
ii linux-image-generic 5.4.0.96.100 amd64 Generic Linux kernel image

Anyway, I had to quickly get this down before rebooting to see if all is good.

[phonic-otg]

Woo-Hoo, everything seems to be restored!
Though, I am not sure what did it. It may have been the code, or it may have been the updates.
Both Info Centre and "uname -r" show the new kernel 5.4.0-96-generic to be operating.
I'll mark this as solved. Thanks to those who responded and kept me seeking out a solution.
Now when I upgrade my Lenovo M.2 SSD to 1TB and RAM from 8GB to 16GB I will use the Micro SD-card as an alternative back up storage. I may mess around with the 512GB SSD in an external case with a full distro of NEON.

EDIT: Almost had to remove "solved" and eat humble pie.
After 3 successful logins, I decided to turn on the pretty sddm login (installed via the inbuilt "Get More" when I first installed the OS to the MicroSD-card), I had reverted to the default login during this issue, and BAM the next reboot has the same issue as what created this thread, even startx from the TTY no longer worked again.
I thought if I could recreate the previous steps from post 12, first removing any login from settings with sddm.
I --reinstalled 5.4.0-96-generic, and did the sed attempt to write to grub and got an error, so I researched it and apparently the command is written wrong. Deciding to just manually edit /etc/default/grub with

GRUB_CMDLINE_LINUX_DEFAULT=".*[^"]/& amd_iommu_dump=1/g"

saved it and then

update-grub

on reboot I got a login screen again.
Very weird, it was the sddm login that re-broke the fix, as from kernel 5.4.0-26 to 5.4..0-92 there were no issues with it.

[phonic-otg]

Sad to say, it looks like I am eating humble pie. None of the attempted fixes stick. I could really use some help.

[Snowhog]

EDIT: Almost had to remove "solved" and eat humble pie.
After 3 successful logins, I decided to turn on the pretty sddm login (installed via the inbuilt "Get More" when I first installed the OS to the MicroSD-card), I had reverted to the default login during this issue, and BAM the next reboot has the same issue as what created this thread, even startx from the TTY no longer worked again.

Emphasis added.

It would seem to me that the 'pretty sddm login' you installed is the cause of the problem.