I self-host Immich on a personal home server. I do pay for backups, though. For 65GB of images (not a lot) I pay ~$1/mo to Backblaze. The backed-up data is 30% bigger in size right now (= 82GB), as it's incremental.

Which means it's not "painless". The immich part may be, but compared to automatically synchronizing to iCloud or Google Photos, the experience is significantly worse for an average user.