The screen locker is broken and unlocking is not possible anymore

[MartinDT]

apt list --upgradable
Listing... Done
apparmor/noble-updates 4.0.1really4.0.1-0ubuntu0.24.04.8 amd64 [upgradable from: 4.0.1really4.0.1-0ubuntu0.24.04.7]
dmidecode/noble-updates 3.5-3ubuntu0.2 amd64 [upgradable from: 3.5-3ubuntu0.1]
dnsmasq-base/noble-updates 2.91-0ubuntu0.24.04.1 amd64 [upgradable from: 2.90-2ubuntu0.4]
libapparmor1/noble-updates 4.0.1really4.0.1-0ubuntu0.24.04.8 amd64 [upgradable from: 4.0.1really4.0.1-0ubuntu0.24.04.7]
libaudit-common/noble-updates,noble-updates 1:3.1.2-2.1ubuntu0.1 all [upgradable from: 1:3.1.2-2.1build1.1]
libaudit1/noble-updates 1:3.1.2-2.1ubuntu0.1 amd64 [upgradable from: 1:3.1.2-2.1build1.1]
libpciaccess0/noble-updates 0.17-3ubuntu0.24.04.3 amd64 [upgradable from: 0.17-3ubuntu0.24.04.2]
xserver-xorg-core/noble-updates 2:21.1.12-1ubuntu1.8 amd64 [upgradable from: 2:21.1.12-1ubuntu1.6]

[Gabriel M]

I managed to fix the issue where Plasma would crash upon login, leaving only a black screen and the cursor. The problem stemmed from two desktop widgets—"org.kde.MinimalMusic" and "org.zayronxio.vector.clock"—as well as an issue involving Fontconfig and the graphics engine (specifically `libfontconfig.so.1` and `libQt5XcbQpa.so.5`). The failure occurs right when Plasma attempts to process fonts or render a visual component (such as `QQuickLabel`) during startup; this can be caused by a corrupted user font cache or a font configuration file that is breaking Qt.

To resolve this problem once and for all, we do the following. We are going to regenerate the system font cache and completely clear the user font temporary files:

1. Let's ensure there are no Plasma processes running in the background:

killall plasmashell

2. Clear the user icon cache, as it may have become corrupted and caused segmentation faults:

rm -rf ~/.cache/fontconfig

rm -rf ~/.cache/icon-theme.cache

3. We regenerated the font cache at the system level:

sudo fc-cache -f -v

4. We restart Plasma:

plasmashell &

5.And if we see that Plasma no longer crashes, we perform a full system reboot so that everything loads normally:

sudo reboot

This is what finally worked for me; I hope it helps those who might be having a similar problem.

I was able to do all this because I had access to the terminal from the desktop using Ctrl + Alt + T; if you don't have access to the terminal, try Ctrl + Alt + F3, but skip step 4 and go straight to step 5.

Greets.

[claydoh]

To resolve this problem once and for all, we do the following. We are going to regenerate the system font cache and completely clear the user font temporary files:

Do you use Google Chrome?

https://www.reddit.com/r/Kubuntu/com...rome_corrupts/

https://issues.chromium.org/issues/565052667
https://issues.chromium.org/issues/565132857

Until Google updates Chrome (today?) it might be worth using a different browser for a short while.

[Gabriel M]

Do you use Google Chrome?

https://www.reddit.com/r/Kubuntu/com...rome_corrupts/

https://issues.chromium.org/issues/565052667
https://issues.chromium.org/issues/565132857

Until Google updates Chrome (today?) it might be worth using a different browser for a short while.

Thanks for the tip. You're right—the problem started when I launched Chrome. I'm not sure if Opera is also an issue, given that it's based on Chromium (I only use those browsers for testing), but Firefox is my main browser. Like you said, it's best to wait until those issues are fixed.

[claydoh]

I'm not sure if Opera is also an issue, given that it's based on Chromium

This seems specific to Chrome proper, not Chromium so I think the derivative browsers probably aren't causing this.

[skyfishgoo]

there was at least one user caught up in this who reported using Brave as their browser