try a modified command - it is just supposed to list any packages named like xxyyzz-git
pamac search -iq git | grep -e “-git”
or
pamac search -iq git | grep “git”
the last one will also find the git package itself - don’t remove that
I have installed updates via “Add/remove software UI” which has warned me some nvidia package will be removed and some other is unable to be installed. I didn’t read carefully and now I cannot boot my PC.
In TTY2, I have executed plasmashell to get
qt.qpa.xcb: could not connect to display
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem
I have tried all of the following, with no luck:
sudo pacman -S mhwd-db
sudo pacman -S nvidia-utils
sudo pacman -Syu plasma-desktop
sudo pacman -Syyu libxcb lib32-libxcb qt5-base
I really don’t remember the exact name of the package being removed and I need my PC to work!
No timeshift backup either 
I did:
pamac search -iq git | grep -e “-git”
or
pamac search -iq git | grep “git”
no result
that is a result, though 
you now know that you don’t have any -git packages installed
ok thanks. Then what do I do next?
I have no idea.
I have no idea why @alireza138812 said what he said, no idea what it was supposed to accomplish.
Then @philm chimed in and suggested to look for -git packages because there apparently was an issue with these.
This lead to a not fully correct command to do that check
and I just provided the working command so you wouldn’t get an error but could do the actual check for the presence of -git packages.
Since that check has now revealed that you don’t have any -git packages installed, that possible reason for your issue is now ruled out.
That is all I know.
I have absolutely no idea why or how an update you did would cause “no desktop”.
Sorry!
looking into system logs (like with journalctl -f in a terminal or in a TTY) or into the log for the KDE session or into ~/.xsession-errors could be helpful
something obviously fails - and there should be traces of it in the logs somewhere
or try updating again - perhaps your update was a partial one and caused your issue?
don’t know - I’d definitely try that first
Thank you for your help. I will definitely try this some time but at the moment I am afraid to update anything. Am running Xfce now it works, and until I have more courage, will leave well alone. It was the very first time an upgrade got me in such a mess and has left me very insecure. I need my computer and only run Manjaro. But thank you, very much appreciated