USB WiFi adapter is not connecting

[orbanp]

Hello Everyone,

I changed ISP providers and at the moment I do not have a wired network connection to my desktop machine. For the time I use tethered USB internet connection through my phone. I would like to use WiFi.
This is my system:

Operating System: Kubuntu 24.04
KDE Plasma Version: 5.27.12
KDE Frameworks Version: 5.115.0
Qt Version: 5.15.13
Kernel Version: 6.8.0-60-generic (64-bit)
Graphics Platform: X11
Processors: 6 × Intel® Core™ i5-8500 CPU @ 3.00GHz
Memory: 7.6 GiB of RAM
Graphics Processor: Mesa Intel® UHD Graphics 630
Manufacturer: Acer
Product Name: Veriton X6660G

I got a tp-link Archer T2U Plus USB WiFi adapter, it uses the Realtek RTL8821AU chipset.
Plugging in the adapter shows up in the "lsusb" command.

I installed the driver from GitHub based on the instructions from this web-site: [HTML]https://moisescardona.me/installing-the-rtl8821au-driver-in-ubuntu-linux-to-use-our-tp-link-t2u-nano-ac600-wireless-adapter/
[/HTML]

The driver shows up in the "dkms status" command:

$ dkms status
rtl8821au/5.12.5.2, 6.8.0-60-generic, x86_64: installed

I can specify in the "Connections - System Settings" a WiFi connection with the SSID and password, yet the system does not pick up the adapter when unplugging/re-plugging or rebooting.
"iwconfig" does not see the adapter either.
Something is still missing.

The adapter works fine under W10.

Any help would be appreciated!
Thanks, Peter

[claydoh]

Look at the actual git page for information:
https://github.com/morrownr/8821au-2...21auko--rocket

The newer standards compliant driver code may be preferable:
https://github.com/lwfinger/rtw88

Also, installing the HWE kernel (6.11) might be valuable in addition to the better driver
Or running 25.04, where the driver is in-kernel (6.14)

[orbanp]

Thanks for the help!

I did read the git page for 8821au-20210708, I think the page I was referring for installation is based on the git page, with a bit less clutter.
I also did install the rtw88 driver previously, same results though.

Other part of the story is that first I got a D-Link AC1300 MU-MIMO Wi-Fi Nano USB Adapter - DWA-181, it is also based on the same Realtek chipset.
It worked, sort of, even on Linux. As it turned out the transmission froze up after a while, even on W10.
When I installed the driver update in Linux, and it still did not work properly, I ran the "remove-driver" script, I think it was for the 8821au-20210708 driver. It must have removed something else also that the GitHub drivers do not include. Since then the USB adapters do not work in the Linux installation.
Any guess what might have been removed?

I did return the faulty D-Link adapter and replaced it with the tp-link adapter.

Thanks, Peter

[claydoh]

I have no idea. I'd look at blacklists, those might be left behind.
I have has an adapter with this chipset in the past but don't recall specifics-- it has been a while. I usually avoid Realtek like the plague for USB wifi, to be honest, if there is no in-kernel driver for the thing.
There have been cases in the past where the same hwid on the same brand and model of device with the same chipset have slightly different revisions, so one does not work in Linux.

I have zero idea what was removed for you. You might need to ask on the relevant github Issues section.

[orbanp]

Some progress and questions.

I tried to install the HWE kernels, it partially succeeded. It failed with an error because of the differing gcc versions.
However, when rebooting, the system booted with the new kernel, but the boot failed with the "vns: unable to mount root fs" error message.
While fixing this error and booting with the older 6.8.0-62-generic kernel I was surprised to that the USB-WiFi adapter was working just fine.
I fixed the kernel panic but the WiFi adapter is still not working with the new kernel.
These are the kernels that I have now:

~$ apt list --installed | grep linux-image

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

linux-image-5.4.0-146-generic/now 5.4.0-146.163 amd64 [installed,local]
linux-image-6.8.0-57-generic/noble-updates,noble-security,now 6.8.0-57.59 amd64 [installed,auto-removable]
linux-image-6.8.0-60-generic/noble-updates,noble-security,now 6.8.0-60.63 amd64 [installed,automatic]
linux-image-6.8.0-62-generic/noble-updates,noble-security,now 6.8.0-62.65 amd64 [installed,automatic]
linux-image-generic/noble-updates,noble-security,now 6.8.0-62.65 amd64 [installed,automatic]
linux-image-unsigned-6.11.0-061100-generic/now 6.11.0-061100.202409151536 amd64 [installed,local]
linux-image-unsigned-6.15.0-061500-generic/now 6.15.0-061500.202505260036 amd64 [installed,local]

When booting with the older kernel I tried to edit the grub file to make this working older kernel the default as described on a number of web-pages.
This does not seem to work for me, the system still starts with the latest kernel as default.
I would be inclined just to remove the newer kernels.

Any comment on the above?

Thanks, Peter

[oshunluvr]

I've experienced similar issues in the past with older hardware. Bottom line is if the newer kernels aren't working with a piece of hardware, then they aren't making things better for you - delete them. If 6.8 works, remove all the others (5.4 and 6.11, 6.15).

It does kinda sound like some package or another hasn't been updated to match the newer kernel versions, but honestly if you're satisfied with 6.8 I wouldn't waste the time to run it down.