I recently found nc-photos [1] which also aims to reproduce the Google Photos UX. It does its own indexing so it is a bit faster than the Nextcloud Photo Gallery but probably way slower than Photoprism. The main advantage of nc-photos is that no software installation on your server is required. It just works as a mobile app with an existing Nextcloud instance.
[1] https://gitlab.com/nkming2/nc-photos