@jacket@tech.lgbt yep, it's an important aspect of (instance) hosting. I've tried a bunch of backup solutions but Borg has been the nicest by far, since you can do append-only (pwned server can't delete it's own backups), encrypted, deduplicated and compressed backups which saves a lot of space.

For hosts i've had a few different solutions; https://borgbase.com, a https://buyvm.net server with a storage slab (usually sold out, try https://buyvmstock.com/ to get notified), and a Hetzner storage box (currently using their borg integration, but considering just sshfs mounting it on a vps and borg'ing to that). My VPS'es back up to the remote backup servers, but also to a machine at home.

On my non-NixOS machines I use the borgmatic wrapper to store/run it's config