How about giving a bit more details about your system? See the red text in my signature...

Any answer to this?
I had the same problem yesterday; unable to logout so logged out via terminal.
Then today unable to login; desktop just blank before actual login page.
Tried a new user; no luck.
Before I reinstall, is there a possible answer to this? How can I reinstall the desktop environment from terminal during startup without messing with any other files?

Just to make sure that all the details are there.
KDE Plasma 5.19.5
Kde Frameworks 5.74.0
QT 5.14.2
Kernel 5.8.0.25 @ 5.8.0.28
OS 64bit
Intel i7-4720HQ
Graphics Mesa DRI Intel HD Graphics 4600

Being impatient : I decided to see what happens when I do as if Plasma is not installed at all.
Installed tasksel then kubuntu-desktop.
Nothing happened; so see if sddm is installed: select sddm. Nothing so it must be still there.
dpkg-reconfigure sddm
Bingo. Starts up and is working.

But why this problem? What went wrong. The desktop looks exactly as it was configured, nothing changed.

I have no idea why, what did you change from the default installation?

FWIW: if a log out doesn't work there is always the possibility t switch off the computer, but usually it is the result of something not configured correctly.

The only changes, outside of adjustments to the presentation of the desktop, I made to the system were a few additional programmes from the software centre and some of my own.
Having said that, there is one potential culprit, Wine. I installed it and because that annoying wine glass kept popping up without being called, de-installed it again.

There is one other thing. In my effort to get the system to boot again, I used the recovery mode and checked the packages. That made no difference. I sudoed update and upgrade without any sign of activities. I did a --fix-missing; nothing. And yet when I re-installed the desktop as mentioned before it worked again.
Does this mean that the hook to the desktop packages was corrupted and if so why is it not found.
I can imagine that installing Wine would alter something in the hooks to the plasma programmes but why are they not returned to the original setting when the programme is uninstalled.

No, this just means that somewhere in your installation a configuration was not completed, that can happen sometimes, that's why (in apt based systems) a

Code: Select all

dpkg --configure -a

is usually a good idea.