I've got this setup recently via pipewire! With something like barrier for kvm, it's great!

I have an alias on each side -- one gets a new source, the other a new sink.

  audio_recv='pactl load-module module-native-protocol-tcp port=4656 listen=0.0.0.0'
  audio_send='pactl load-module module-tunnel-sink server=target:4656'

This used to require Nohands I think on Linux. But iirc I think somehow Bluetoothd and pipewire can maybe just do this somehow now? I'm quite surprised it works for three systems at once though! Neat. https://nohands.sourceforge.net/

My Lenovo Tab Plus tablet works as a Bluetooth speaker. Bought it because it was crazy cheap and has amazing amazing speakers.

Overall we are deeply misserved by the weird casting of devices being for this or that. Computers are flexible & general purpose & should in most cases be willing to act as peripherals for other systems. Onwards, until maybe some day: the network is the computer.