AppImages cannot work with Pipewire properly.
The reason is that AppImages contain all libraries statically linked into themselves.
Pipewire works by switching the ALSA, Jack and Pulse libraries under the seat of the applications without them noticing.
(Pipewire does access the original ALSA itsself, but for all other apps, it replaces it.)
This replacement trick cannot work with AppImages. Technically impossible to my knowledge. Not the fault of Pipewire, but of the AppImage design principle.
I filed a ticket with OSM regarding the issue.
So, OSM will only work for ALSA devices (as it has old ALSA linked into it) that are not set to proaudio in Pipewire und thus not are exclusively blocked. Technically those will be accessed bypassing Pipewire.
It does not work very well.
The solution I didn't manage to do yet is to compile OSM yourself, not statically linked. But I do not understand their build syystem.
https://github.com/psmokotnin/osm/issues/127
