Package: wireplumber Followup-For: Bug #1032351 Control: close -1 After rebooting the system, sound is available again.
Various other user-context systemd files appear to be missing; I don't think those were removed from the system manually, but nor can I confirm yet what the cause was (if I can, and if there is a bug, then I'll open a separate bug for that). Apologies for what seems to have been an unnecessary bugreport and/or operator error.