Immich recently had a bug where it would delete all the photos if you remove a gallery. It has breaking changes and API changes all the time. Why? I don't know. You do NOT need to break the API every other minor version, it's super dumb.

That makes it impossible to use it with other users because I can't control how and when their mobile app gets updated, which means at any given time I have no idea if their apps will work with the server version. And when they do work, they're buggy.

You can use it just for yourself if you're very careful but it's not something I can offer friends or family and promise it's better than Google Photos or iCloud. Not if it doesn't work half the time and may delete their photos every once in a while.

A simple alternative is to use a sync app to upload photos from a person's phone and then use a reliable (doesn't break all the time) photo webapp to let them browse them. They can still manage their photos locally, and use other services, and other backups and so on, they just have an extra backup + viewer.