Generally this means the kscreenlocker_greet process has crashed. And if something crashed, we need a backtrace of it so we can figure out what's going on. Can you please attach a backtrace of the crash using the `coredumpctl` command-line program, as detailed in https://community.kde.org/Guidelines_and_HOWTOs/Debugging/How_to_create_useful_crash_reports#Retrieving_a_backtrace_using_coredumpctl?

Thanks!

Dear Bug Submitter,

This bug has been in NEEDSINFO status with no change for at least
15 days. Please provide the requested information as soon as
possible and set the bug status as REPORTED. Due to regular bug
tracker maintenance, if the bug is still in NEEDSINFO status with
no change in 30 days the bug will be closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

If you have already provided the requested information, please
mark the bug as REPORTED so that the KDE team knows that the bug is
ready to be confirmed.

Thank you for helping us make KDE software even better for everyone!

Created attachment 167913 [details]
Journalctl Log

Nothing in coredumpctl at all. I've just replicated the issue now and no crashes at all from the current day.

I figured I'd check journalctl and grabbed 10 minutes of where it happened and I saw in there: Mar 29 19:46:27 lenovo-laptop kernel: kscreenlocker_g[3795669]: segfault at 8 ip 00007f552a6b6598 sp 00007ffef2fc9d80 error 4 in libPlasmaQuick.so.6.0.3[7f552a68b000+4c000] likely on CPU 4 (core 2, socket 0)

The whole log is attached, as Bugzilla has a comment limit size.

Dear Bug Submitter,

This bug has been in NEEDSINFO status with no change for at least
15 days. Please provide the requested information as soon as
possible and set the bug status as REPORTED. Due to regular bug
tracker maintenance, if the bug is still in NEEDSINFO status with
no change in 30 days the bug will be closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

If you have already provided the requested information, please
mark the bug as REPORTED so that the KDE team knows that the bug is
ready to be confirmed.

Thank you for helping us make KDE software even better for everyone!

Derp, you even mentioned there was no crash, sorry for bad reading comprehension.

This stuff all looks relevant to me:

Mar 29 19:46:27 lenovo-laptop kscreenlocker_greet[3795669]: qt.qpa.wayland: eglSwapBuffers failed with 0x300d, surface: 0x0
Mar 29 19:46:27 lenovo-laptop plasmashell[2700339]: kf.windowsystem.wayland: Failed to recreate shadow for NotificationPopup_QMLTYPE_395_QML_399(0x55700fb34c40)
Mar 29 19:46:27 lenovo-laptop plasmashell[2700339]: qt.qpa.wayland: eglSwapBuffers failed with 0x300d, surface: 0x0
Mar 29 19:46:27 lenovo-laptop kernel: kscreenlocker_g[3795669]: segfault at 8 ip 00007f552a6b6598 sp 00007ffef2fc9d80 error 4 in libPlasmaQuick.so.6.0.3[7f552a68b000+4c000] likely on CPU 4 (core 2, socket 0)
Mar 29 19:46:27 lenovo-laptop kernel: Code: cc cc 55 48 89 e5 48 8b 47 28 48 8b 40 08 48 8b 40 10 48 8b 40 38 5d c3 cc cc cc cc cc cc cc cc cc cc 55 48 89 e5 48 8b 47 28 <48> 8b 40 08 48 8b 40 10 48 8b 48 10 48 85 c9 74 20 8b 49 04 85 c9
Mar 29 19:46:27 lenovo-laptop kernel: audit: type=1701 audit(1711703787.190:807): auid=1000 uid=1000 gid=1000 ses=3 subj=unconfined pid=3795669 comm="kscreenlocker_g" exe="/usr/lib64/kf6/kscreenlocker_greet" sig=11 res=1
Mar 29 19:46:27 lenovo-laptop kwin_wayland_wrapper[3615]: not a valid new object id (2), message get_registry(n)
Mar 29 19:46:27 lenovo-laptop kwin_wayland_wrapper[3615]: error in client communication (pid 3615)
Mar 29 19:46:27 lenovo-laptop kwin_wayland_wrapper[3796335]: error: received delete_id for unknown id (84)
Mar 29 19:46:27 lenovo-laptop kwin_wayland_wrapper[3796335]: error: received delete_id for unknown id (77)
Mar 29 19:46:27 lenovo-laptop kwin_wayland_wrapper[3796335]: error: received delete_id for unknown id (74)
Mar 29 19:46:27 lenovo-laptop kwin_wayland_wrapper[3796335]: error: received delete_id for unknown id (29)
Mar 29 19:46:27 lenovo-laptop kwin_wayland_wrapper[3796335]: error: received delete_id for unknown id (28)
Mar 29 19:46:27 lenovo-laptop kwin_wayland_wrapper[3796335]: wl_display@1: error 1: invalid arguments for wl_display@1.get_registry
Mar 29 19:46:27 lenovo-laptop kscreenlocker_greet[3796335]: qt.qpa.wayland: Loading shell integration failed.
Mar 29 19:46:27 lenovo-laptop kscreenlocker_greet[3796335]: qt.qpa.wayland: Attempted to load the following shells QList("layer-shell")
Mar 29 19:46:27 lenovo-laptop kscreenlocker_greet[3796335]: qt.qpa.plugin: Could not load the Qt platform plugin "wayland" in "" even though it was found.
Mar 29 19:46:27 lenovo-laptop kscreenlocker_greet[3796335]: This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.
Mar 29 19:46:27 lenovo-laptop kernel: audit: type=1701 audit(1711703787.341:808): auid=1000 uid=1000 gid=1000 ses=3 subj=unconfined pid=3796335 comm="kscreenlocker_g" exe="/usr/lib64/kf6/kscreenlocker_greet" sig=6 res=1
Mar 29 19:46:27 lenovo-laptop kscreenlocker_greet[3796360]: qt.qpa.wayland: Loading shell integration failed.
Mar 29 19:46:27 lenovo-laptop kscreenlocker_greet[3796360]: qt.qpa.wayland: Attempted to load the following shells QList("layer-shell")
Mar 29 19:46:27 lenovo-laptop kscreenlocker_greet[3796360]: qt.qpa.plugin: Could not load the Qt platform plugin "wayland" in "" even though it was found.
Mar 29 19:46:27 lenovo-laptop kscreenlocker_greet[3796360]: This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.
Mar 29 19:46:27 lenovo-laptop kernel: audit: type=1701 audit(1711703787.423:809): auid=1000 uid=1000 gid=1000 ses=3 subj=unconfined pid=3796360 comm="kscreenlocker_g" exe="/usr/lib64/kf6/kscreenlocker_greet" sig=6 res=1

I can't reproduce this issue with current git master when I do the following:

1. Plug laptop into USB-C dock and plug an HDMI screen into the dock
2. Open Kickoff > Click "Sleep"
3. Unplug the USB-C dock
4. Wake up the laptop

No screen locker crash.

Can you write detailed steps to reproduce that include mention of your hardware setup?

Dear Bug Submitter,

This bug has been in NEEDSINFO status with no change for at least
15 days. Please provide the requested information as soon as
possible and set the bug status as REPORTED. Due to regular bug
tracker maintenance, if the bug is still in NEEDSINFO status with
no change in 30 days the bug will be closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

If you have already provided the requested information, please
mark the bug as REPORTED so that the KDE team knows that the bug is
ready to be confirmed.

Thank you for helping us make KDE software even better for everyone!

This bug has been in NEEDSINFO status with no change for at least
30 days. The bug is now closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

Thank you for helping us make KDE software even better for everyone!