Yes, absolutely. I move between two sites, and also run some gear at my sibling's home, so I have the 3 separate sites thing sorted. ECC + RAID1 + borg at each site gives archival capability on top of standard backup.

Syncthing has the 'untrusted peer' feature, which I've only used once, accidentally, but I believe provides an elegant way of providing some disk for a friend while maintaining privacy of the content.