Palettes invisible in MuseScore 3.4.2 (linux)

Hi!
I have been using MuseScore for quite some years now, running linux on my computer (Solus). I installed it from the OS's repository.
Since a few versions back I have not been able to make the "palettes" visible when using MuseScore.
In the menu they are ticked but they remain invisible.
When I also tick "all palettes" (or whatever it's called in English, I'm running the German version) I can get those onto my screen but only as a free-floating window, I cannot attach them anywhere or resize them, so that window is always in the way and I have to keep pushing out of the way.

Are the invisible palettes a known bug?

I'm really lost here as I don't know how to get the palettes back and use them as intended.
Please help!

Thank you very much, also thanks for a fantastic notation program!
Jörg Walesch