"Who's still left in the home backup solution ring? Besides iCloud/Google Drive/Dropbox, I count...Backblaze? And that's it? "

If you are a unix user and/or reasonably technical, I think rsync.net would be the best choice.

You get an empty ZFS filesystem, possibly with snapshots enabled, that you can do whatever you like with (provided "whatever you like" is something that runs over SSH...).

Pointing borg/rclone/restic/git-annex/etc. to rsync.net works exactly the way you'd think it would.