I don’t know since when, but I cannot control any application volume anymore from within them. If I open Rhythmbox, VLC or Youtube on Firefox I cannot mute the sound or change the volume using their interface.
Due to this muting tabs on Firefox no longer works, as well as any site that has autoplay enabled now plays it with sound (Reddit for example)
I can change the volume normally system wide, though.
I’m using 5.16.19-200.fc35.x86_64 with GNOME on Wayland, and I’ve got no idea what caused this or how to solve it.