I have recently repurposed and old Hp Stream to a home server and successfully run Immich. I really like it and even a small 500GB disk is way more than the 15GB Google offers.
My issue though is about backup. I would only be comfortable if all the data is backed up in an off-site server (cloud). But the back up storage will probably cost as much as paying for a service like ente or similar, directly replacing Google photo.
What am I missing? Where do you store your backup?
If you have 1tb+ of data you can get a cheaper option just by moving to hetzner (also, even storj is cheaper than backblaze)