This is unacceptable, just give us back this functionality and create whatever internal ticket you need to. You work for Spotify, not us. We are your customers and we want this fixed since it isn’t a new feature and already worked fine before the last update.
Please direct users to the existing idea so they can like it. There are 54 likes on the original support topic and currently only 9 on the "idea". Is there something you can do to let those 54 people know that there is something new they have to like in order to resolve this? It seems like it's going to be very difficult to get a decent representation of the people who want this back without your help. https://community.spotify.com/t5/Live-Ideas/All-Platforms-Cross-device-Volume-Control/idi-p/5045278#