I came here to say the same thing except that I have a pi locally and one at a relative’s house. I back up to the local pi and a nightly cron starts rsync to pull my local copy.

I chose this so that i could control the rstnc start time, bandwidth and stop time but also so I could leave the remote network vanilla with no open ports, etc. With bandwidth limiting, it may take a few days to catch up from full backups, but a differential is same day.

Be sure to use a RO filesystem or overlay FS on the Pi card. I’ve had them go corrupt.