I recreated the template VM(using your commands, but excluded blueman) and changed my sys-audio’s template to the new template. It’s getting other VM’s streams in “Playback”, but it didn’t properly utilize my soundcard. It’s “Dummy Output” in “Output Devices”.
I then backup’ed sys-audio, deleted it and created a fresh AppVM, calling it sys-audio(to avoid playing with policies), and adding sevice “audiovm”. It’s also automatically receiving streams from newly started VMs. I didn’t even manually start the daemon! Although “Output Device” was still a mess. But that doesn’t seem to be your problem.
When I switched my newly created sys-audio’s audio back to deb11-min-audio (the old template), my soundcard was working again. So the main difference between the two templates is the soundcard problem. If this isn’t your problem, then I’m afraid I cannot reproduce your problem.