_PGK_

(Hopefully) working solution:

I wrote a following bash script:

#!/bin/bash
rm ~/.minecraft/webcache2/Default/Preferences
minecraft-launcher &

And replaced minecraft-launcher with the script location in the .desktop file (alternatively you can just run the script directly). The script must have an “executable” attribute set. This can be done either by right-clicking on the file, going to preferences, permissions and checking the “executable” checkbox, or running a command chmod +x <script-filename>.

Explanation:
The launcher seems to clash with plasma-integration extension, and the simplest way to fix it is removing the browser’s preferences file (located by default in ~/.minecraft/webcache2/Default/Preferences).

First line of the script says its a bash script (should be executed by /bin/bash).
The second line removes the file ~/.minecraft/webcache2/Default/Preferences
The third line launches the minecraft-launcher and closes the script without waiting (the & character in the end) so it doesn’t stay open the whole time you play.

Hope this helps, it worked for me.