I have an external storage unit a couple kilometers away and two 8TB hard drives with luks+btrfs. One of them is always in the box and after taking backups, when I feel like it, I detach the drive and bike to the box to switch. I’m currently researching btrbk for updating the backup drive on my pc automatically, it’s pretty manual atm. For most scenarios the automatic btrfs snapshots on my main disks are going to be enough anyway.