I've recently install KDE Plasma as my main DE; but I can't seem to get it working. The desktop's installed fine, it just won't start up! I clicked on the bottom-right gear at login, selected KDE Plasma, and login... but it just locks me out, and brings me back to the user menu. 
Hi, What version of Zorin are you currently running and how did you install Plasma?
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I am using Zorin 16.3 Core; desktop installed using sudo apt install kde-plasma-desktop
Also changing DE locks me out with every other DE that's not Wayland; even Xorg
Ok, that is the wrong way to install kde! Use Zorin Default desktop, open a Terminal (Ctrl+ Alt+ T) and enter:
sudo apt-get remove kde-plasma-desktop
After it has been removed, enter:
sudo apt-get update && sudo apt-get full-upgrade
Then restart the machine.
Again after restarting, open a terminal and enter:
sudo apt install kde-full
Then do the update commands again and reboot.
When at login after you have selected user, go to cog and select 'Plasma'.
Ty, ill try
that didn't work....
Did the remove command work?
I don't think it did.
Ok, from terminal try this:
sudo apt purge '^kde' '^plasma'
Yes that deleted it.
There were some Failed to removes though
What were the fails?
Just Google Chrome packages which have actually been deleted, it probably didn't exist in the first place because I have never touched that browser. I use Firefox.
You can try reconfiguring GDM3 since I believe SDDM is used by Plasma:
sudo dpkg-reconfigure gdm
Once configured, run
sudo apt --fix-missing install
sudo apt-get install -f
To ensure any necessary D.E. dependencies are installed.
There may be a configuration file that is causing the issue. You can try (This will result all your custom D.E. Settings to default. By creating the -bk file, you are creating aback up which can be restored:
mv ~/.config ~/.config-bk
Log out and in, then log out and try logging in on Plasma D.E.
2 Likes
Ok, thank you!
What?:
When I run sudo dpkg-reconfigure gdm, it says this:
dpkg-query: package 'gdm' is not installed and no information is available
Use dpkg --info (= dpkg-deb --info) to examine archive files.
/usr/sbin/dpkg-reconfigure: gdm is not installed
I'm not continuing to run the other commands that you told me to, because the previous one failed. How do I install gdm? 
Sorry, dropped the 3
sudo dpkg-reconfigure gdm3
T.Z. -6 hours GMT