It is very strange that this problem keeps coming back, just when things seem to be going well.
@MichaIng You said that
I installed Opera stable completely freshly, did not migrate my profile, setting or any such, and after some days/weeks of usage, the issue reappeared.
that's why I don't even feel like trying to set up a new profile 😂
When I added this to my Opera startup link, permissions remained stable for maybe a week, before the issue reappeared.
I can check that, I'll try running the browser that way for as long as possible. It might not work, however, because the browser can be launched via other triggers without the -disable-features=DIPS flag.