Installed Sequoia, getting prompted for authentification for EVERYTHING

Hi everyone!
I eventually installed Sequoia on my Macbook Pro 2013. Works pretty fine except that I'm getting prompted for authentification for just everything!
Wanna empty the bin? enter your password. Wanna move a file from the desktop into a folder on the desktop? enter password. Wanna edit a Pages file? Duplicate it. Oh wait, you don't have permission to do that!

I only have one user session, of course it's an admin session.
Checked folder authorizations with Cmd+I, they are not locked, I have rights to read and write.

Tried repairing authorizations with Onyx but can't find that option in that version… Disk Utility doesn't offer it either.

I had first enabled File Vault but quickly turned it off. (of course i've rebooted maaaaaany times as you can imagine…)

I've browsed Reddit with no success. Any idea? Thanks!