I don't have nearly that much worth backing up(5TB--and realistically only 2TB is probably critical), but I have a Synology Nas(12TB raid 1) and truenas (zfs striped/mirrored) that I back my stuff to (and they back up to each other).
Then I have a raspberry pi with a USB drive (8tb) at my parents house 4 hours away, that my Synology backs up to (over tailscale).
Oh, and I have a USB HDD(8tb) that I plug in and backup my Synology Nas to and throw in my fireproof safe. But thats a manual backup I do once every quarter or 6 months if I remember. That's a very very last resort backup.
My offsite is at my parents.
And no, I have not tested it because I don't know how I'm actually supposed to do that.