OK, after wasting several hours on this, the simplest solution turned out to be:
-
Reinstall debian-12-minimal template, thus getting rid of stuff which the upgrade installed in templates (including pipewire)
-
Clone the template to debian-12-player
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In the clone:
apt-get install --no-install-recommends thunar mpv pulseaudio-qubes
- Configure mpv in the AppVM based on debian-12-player:
$ cat ~/.config/mpv/mpv.conf
vo=x11
profile=sw-fast
- Enjoy again full screen 1080p flawless playback