Most docker templates have a host path for data that the docker would access or write too. For PS you might need multiple (I elected to because it was the sorting I wanted to use from PS - so one to scan and another share to write too, the later is already in the template). So the host path for photos with the explanation this is existing media to be scanned by ps would be sufficient.
You could leave blank for the user to define a specific share or prepopulate with /mnt/user. That would would work well with the automatic setting in pS because it would give PS access to all shares for scanning. And it would work with the in app settings for a user to define in there the specific shares if they wanted I think.
Nextcloud example pointing to an example share in unraid
what I inserted for PS template
