upgrade to bookworm

have upgraded to Debian bookworm (technically still unreleased, but is now in hard freeze)

mostly a painless upgrade, but had a few problems

1. when starting fluxbox without a display manager, it was failing
2. firefox was very slow to start, and thunderbird was unable to save files
3. sound applications were hanging

I did not diagnose the fluxbox startup, but capitulated and installed a display manager instead. Notably it started a different window manager by default, but that could be changed.

The other two problems were because the xdg-desktop-portal was timing out trying to communicate to pipewire, and pulseaudio also could not communicate to pipewire. This could be seen in the user logs.
This meant that any applications using pipewire to do things such as open a file dialog or talk to audio would fail.

The journal log showed that xdg-desktop-portal was "not starting" and "failed to connect to to bus". In turn, pipewire was reporting "no bus medium found".

Turned out that the reason the pipewire service failed was because the flatpak service was failing. It was reporting ".flatpak-info file is malformed".

In the root folder was a remnant (and empty) .flatpak-info file. Removing this solved the issue (uninstalling/purging and reinstalling flatpak did not remove this file).