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Not sure what app you're referring to since Deezer just doesn't have that feature.

I could be self-hosting though as I'm in the process of setting up a server.

I'm looking for something that does multi-device remote control similar to how Spotify does. Deezer just cancels playback on the other device.

No worries, you explained it well. People will grasp at straws to dismiss any argument if they aren't ready to examine certain convictions.

Would you believe it if they said that it's not actually that bad?

No it doesn't, slavery wastes an insane amount of potential. And this is far more about automation.