Explore Proxmox Backup Serve. You can set up replications of backup sets to an offsite location using Remotes, and this takes advantage of the dedup capability in PBS on the initial backups.
I have also used ZFS for my underlying storage of the backups, and that gets repped to zfs.rent, but it would be a more difficult recovery since I’d have to set up another PBS server and hook the zpools on to it, but not really difficult.
I also have a pair of USB harddrives that I swap on to the PBS server and it runs a separate backup to the USB drives (with the offline one failing, of course). I then swap the drives out weekly and restart the PBS server to initialize the correct datastore for the next weeks backup. I could do that online manually at the CLI, but it’s just as easy to let zfs.mount take care of it at reboot.
Stepsister. Or people will think you’re weird.