+1 to immich
However, because of the fast dev cycle, it has a lot of breaking changes, and needs regular maintenance (most notably for me, postgres docker changes. Especially if you are not giving it it’s own postgres instance and using their provided docker compose.)
You could stay pegged to a single version, but the mobile app also doesn’t have full backwards compatibility with server versions, which results in a slew of other problems (how do I do a fresh install of an older app version on a new device?)
But if you are willing to keep up and perform semi-regular maintenance, immich is great, and the rapid dev cycle means more new features faster!
I don’t remember much about plex photos, but facial (and object) recognition, photo map, easy sharing through albums (without the other person needing an account), and being open source are some features I imagine plex photos does not have.
it seems barebones still, because it is a very young app, and the UI is not great, especially on mobile.
It is the best replacement for Google photos that I have seen though.