I'm also looking for "Google Photos but self-hosted" with the main feature being automatic object detection.

I just tried the Photoprism demo (https://demo.photoprism.app/browse), searched for "person", "grass", "wave", "head", "eye", "neon" and a bunch of other terms, nothing seemed to find any pictures although I took the concepts from existing photos I found.

Back button is also broken on the demo, which makes it seem like the most basic UX is not there yet in the application.

The quest continues...