I backup to a external hard disk that I keep in a fireproof and water resistant safe at home. Each service has its own LVM volume which I snapshot and then backup the snapshots with borg, all into one repository. The backup is triggered by a udev rule so it happens automatically when I plug the drive in; the backup script uses ntfy.sh (running locally) to let me know when it is finished so I can put the drive back in the safe. I can share the script later, if anyone is interested.

It’s been added recently, in the form of External Libraries.

I did not know that, last I looked it was still in development, I believe.

Something that LVM supports but ZFS and BTRFS don’t, is the ability to reduce your storage. (That is, to empty and remove a drive from the array, without having to completely destroy the storage array.) As a home user without sufficient storage to have complete duplicates of everything, I find this an important feature.