@leocg okay the setting I was referring to was about the player, not videos in general.

Still I tried other browsers and ther it works just fine. That's why I asked here, since it seems to me to be a setting issue with my opera browser.

Or do you have any other ideas what might cause this?

I know that there is a setting in "functions" for that. Unfortunatly turning that off did not help at all and the problem still exists even after restarting the browser.

I just want to listen to music while watching a livestream on mute...