Although Immich does backup from your phone, I don't see it as a viable backup solution. Git-annex, Unison, and Syncthing are much better at keeping files synchronized across devices. Immich will create its own copies of photos and transcode videos for playback on the web. That may be fine if you have enough storage space, but for me it makes the phone backup useless. I suppose you could use a git-annex special remote directory as an Immich external library.