for some unknown reason my GUI changed completely from my ‘oldschool’ Windows themed one to a minimalistic one.
As I didn’t initiate it, I have no clue, what to do, to switch it back.
There wasn’t an update yesterday which might have triggered such behavior.
I am sorry for you - but no one can help you with that.
While it is annoying - with computers everything has a reason.
No one can know what except you - your are the only person which knows what is going on your computer - and it is impossible to guess.
With knowing anything about your system - it could be anything - the system can no longer read the required files and therefore it falls back to a fail safe - who know?
Is your theme an actively maintained theme? It could be one or more theme components not compatible with the latest iteration of Qt?
I found the ‘error’ after your mention of the theme.
I login my user automatically. After switching that of and restarting, I saw, that Manjaro, for some unknown reason had switch to Gnome as desktop manager.
I have changed back to Plasma and all is well.