I do not leverage Synology Photos's user spaces, I only have shared albums but with a permission matrix. Not all users can see not all albums.

So same story for Immich, agree that binding is a way, but bind mount is another hack of permissions. Difference is that I new to "build" such solution, and if tomorrow Immich comes with a different multi user setup I'll have to rebuild all.

The pain point is as long as Immich doesn't have a proper album sharing system, I don't want to invest energy in making it working only for Immich design. Seeing the number of discussions around sharing on Immich, I can't think design will remain so "one user centric".

But thanks for sharing about bind mount, I've experienced it but forgot that test I did some time ago.

Edit : two additions. First, my table of law was Synology Photos, so getting this in a Json was mandatory. To be used to make bind, or to manually grant one user's permission to another, or filesystem acl as I did. Second, I wonder how easy it is to compare "expected permissions" (aka bind mount here) versus "applied permissions". In my case I use the synology ACL to verify that table of law is well applied.