Well, I tried to migrate liteqube’s core-sound to 4.3’s pipewire and apparently it does not work. When I run pulsemixer on core-sound, it shows client qube controls attached, but I still hear no sound. I have almost zero experience with audio subsystem, so I have no idea what could go wrong 
I don’t know if it’s relevant to your porting work, but something that tripped me up in assembling an audio-capable debian-13-minimal-based template is that the pipewire-qubes package does not have pipewire-pulse, wireplumber, pipewire as dependencies, yet these are all required for audio to come through in the general case.