Volume control works for VLC but not for spotify. Reproducible: Always
Spotify doesn't expose that feature in MPRIS (the protocol we use to control media players), so we can't do it. It would be nice if you could reach out to them and ask for better MPRIS support: the more people who complain the higher chances to get it :)
I imagined that. I'll try to reach them. Thanks.
Just a brief update on this. This is the reply of one developer of spotify: "Nobody is working on it currently, but it is tracked internally as "Add more MPRIS functionality", that I want to do eventually. There are some linux crash bugs that I want to focus on first. I can set aside one day every two weeks to help fixing bugs in the linux system specific parts of the desktop client. That is roughly the pace of development currently." https://community.spotify.com/t5/Desktop-Linux-Windows-Web-Player/Cannot-control-volume-using-MPRIS-D-bus/m-p/1465152/highlight/false#M167907