First things first, can you boot into the Recovery Console by tapping or holding the left Shift Key - then choosing Advanced Options for Zorin. Select the 5.11.0-27 or 5.11.0-25 kernel.
Try Booting up.
If this does not work,
From recovery menu, arrow key down to Enable Networking
Once done, back up to the Recovery Menu then arrow down to Drop to Prompt
Hit enter
Then
sudo apt install -y zorin-os-desktop gnome-shell
I think I also have some traces of kde left behind. Can I delete them later?
Also, ist the 5.11.0-34-generic okay?
I recommend against it if you are using Nvidia. Today, several threads popped up showing that Nvidia users that updated to the 5.11.0-34 experienced black screen at boot.
If you do not have an earlier version, from the prompt, please run
sudo apt update && sudo apt full-upgrade
and watch if you are offered the 5.11.0-36 kernel, instead.
Yep.
Install Synaptic
sudo apt install synaptic
Once installed and when you are back on your desktop, launch Synaptic. Click the search button on the top toolbar and enter in plasma.
You will see a long list of KDE relevant Plasma Desktop files that are installed.
Select each for removal (remove completely). Once you have made all your selections, click the Apply button on the top toolbar to remove them.
I am booting in the older kernel now. (The -25 one)
I have to boot in recover mode in order to do that. The screen is just black otherwise.
It says it isn't able to find zorin-os-desktop-gnome-shell.
No dash between them^
How. No dashes at all? Cause with no dashes it doesn't work either.
No dash between zorin-os-desktop and gnome-shell
It should look just like I have it above.
I think I have to reinstall.
What command did you use to remove Plasma?
Different ones. Things like "sudo apt purge kde-*". This one was the command after which everything broke. (After reboot)
In reinstalled the gnom shell and bootet into the system normally but everything I see is a black screen with a white flashing cursor.
ummm... that's a tough trail to follow. If you reinstall now, will you lose any important data?
In future; removing a desktop environment is most easily done using Synaptic- as I wrote a quick guide for above.
Your experience here is one I did repeatedly after starting out on Zorin.
It's how I did a lot of learning.
Gnome doesn't start.
The system itself is running and the console works but I have problems with gnome.
I have many packages and much software I would use. Most of the other data is saved on another drive and partition.
I feel your pain... But I agree a reinstall is the best option. I would not want to keep guessing in the dark as to what was removed and increase your problems.
A note for Future self: Don't guess when removing something in terminal.
The * can be deadly.
I'll just try to make a list of the software I had and reinstall it later. Bad thing.