I use Tailscale for this, always connected and Immich pointing at the TS IP. I haven’t yet made the jump to full syncing, so I have a manually curated library of photos that I access anywhere but I am planning on starting to test this feature soon (I take a lot of junk throwaway photos with the phone and don’t want to sync everything). I’ll have to see how it best works for me.

But Immich is a great app, minimal to no fuss setting it up in a container on my NAS. My only potentially unfounded concern is when I upgrade the images. They changed the different component containers images over time, sometime with breaking changes. So I always half expect that an upgrade will screw up the setup and I’ll have to start from scratch with the indexing.