The screen locker is broken and unlocking is not possible anymore

[MartinDT]

this has appeared after rebooting laptop and logging in, when I tried to lock the screen and go AFK

uname -a
Linux martin-inspiron153530 6.8.0-142-generic #142-Ubuntu SMP PREEMPT_DYNAMIC Wed Sep 2 14:24:27 UTC 2026 x86_64 x86_64 x86_64 GNU/Linux

lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 24.04.5 LTS
Release: 24.04
Codename: noble

[skyfishgoo]

why are you using such an old kernel?

7.0.0-34-generic

was just pushed out to me yesterday.

[die.boer]

recover the session

Ctrl+Alt+F3

log in , then

loginctl unlock-session 3

then Ctrl+D and return to the graphical session with the appropriate Ctrl+Alt+F* shown on the screen.
Then, while back in Plasma,run these and post outputs please

/usr/libexec/kscreenlocker_greet --testing

plasmashell --version

echo $XDG_SESSION_TYPE

dpkg -l | grep -E 'kscreenlocker|plasma-workspace|kwin'

journalctl --user -b | grep -Ei 'kscreenlocker|screenlocker|kscreenlocker_greet|kwin|plasmashell' | tail -100

[Ramogsap]

Hi all. New kid here, but with years with (k)Ubuntu.
I'm in the same situation of MartinDT with two PC's.
The uname -a and lsb_release -a are exactly the same as #1

Tried Ctrl+alt+F3
Login

Tried loginctl unlock-session 3
Ctrl+D

Ctrl+Alt+F2 (as it says on the screen error)

but the system cant return to plasma. Only black screen with the mouse pointer.

I tried watever I know, but no results. I'm running out of ideas...

[Gabriel M]

Hi, I'm new here too and have a similar problem to yours. I updated my system yesterday, and after the update, the Plasma environment crashes upon entry; the desktop goes black with the cursor stuck in the center. I accessed the terminal via Ctrl+Alt+F3, cleared the Plasma cache, and moved the Plasma shell files to a temporary backup folder. My desktop reverted to a fresh-install state—even showing the welcome window—but it still crashes and displays the black background. When the screen locks, I get the same message MartinDT mentioned, and I can't seem to restore the Plasma desktop. It's worth noting that the exact same thing happened to another laptop of mine after the latest update.

I have another user account on the same machine, but it wasn't affected and I can log in normally—which is how I'm writing this—so I don't know what happened.

I am using:

Kubuntu 24.04.05 LTS x86_64
Kernel: 6.8.0-142-generic
Plasma 5.27.12
WM: KWin

I hope there will be a solution to this problem soon.

Greets.