Universal control seems to conflict with the Music app's Airplay.
I have two Macs and use Universal Control. As soon as I enable AirPlay in Music App to stream on both Macs, Universal Control stops working.
Example :
Mac 1 (M1) shares keyboard/mouse to control Mac 2 (Intel).
Mac 1 plays Music and enable Airplay to play on Mac 1 and Mac 2.
Suddenly shared keyboard/mouse from Mac 1 cannot "reach" Mac 2.
MacBook Air Apple Silicon