Immich is self hosted only so it doesn’t really need e2ee since you can just encrypt the disk of the server. It also runs a load of on server machine learning stuff for automatic people tagging and search.
Ente is selfhosted (also has a hosted version) but encourages family use so I think that's why they do E2EE. It also does all the ML on the client side for people tagging and search.
Mozilla backed it with a grant but that was a few years ago.
