I've just noticed a similar issue. I haven't seen this over the past four years with my Mac. Here are the details.
I was listening to an audio stream on my Mac and audio suddenly went to mute while I was NOT in front of the Mac. I was unable to control volume and forced close all apps to prevent sound from suddenly spiking (I assumed it was Mac software/hardware.) I opened settings to Sound Output and saw a device, an AppleTV, listed that isn't mine. My AppleID account is fine. Initially this -extremely disconcerting- BUG appears to involve AirPlay, macOS 12.0.1 and an AppleTV (TvOS unknown at this time) NOT belonging to me. (Am I getting ANYONE's attention in AppleLand yet?)I turned on a BlueTooth scanner, and made screenshots of device info (unnamed for now) with high RSSI (nearby). The fact that someone else's AppleTV -even- shows up on my Mac under Settings Sound Output is a problem that I hope Apple software engineers are already aware of and are attempting to fix. WHY was a 'foreign' user device, an Apple device, allowed to contact to audio on my Mac? I cannot and do not want to connect to their AppleTV. WHY was my Mac muted? This 'sharing' security bug is VERY bad, and it's yet another critical security issue involving NFC in my not so humble opinion. I have an AppleTV with AirPlay, but it does NOT broadcast. Another AppleTV owner -should- be able to broadcast, but their device should NEVER appear on a completely different Apple ID account device.
