I’ve searched extensively and there are many mentions of this problem but it seems only a few disparate users have had it over the last few months. But the 3 Kubuntu systems I upgraded to 20.10 all have it now, so I’m surprised it’s not a critical bug with already a solution.
- ‘switch user’ is gone from the K / Leave menu
- ‘Switch user’ is gone from SDDM lock screen (you can only re-enter your own locked session). Shutdown / reboot is also gone from lock screen.
- Maybe unrelated: when logging out some users (always the same ones), I get a black screen (for others I go back to a normal sddm screen with user selection). This is not related to the kde_settings.conf / MinimumUid issue
Out systems are family-shared, so it’s really annoying. If the lock screen is on, the system has to be forcefully rebooted for another user to use it, with all the disk corruption risks involved.