Backend storage is all ZFS. I have a big external drive plugged in via USB on my ZFS box and that backs up my daily backups.
I have a two old PCs that I run ZFS on as well. One auto turns on every week and ZFS backs up to that. The other PC is completely manual and I just randomly turn that on and backup. Every so often. Usually every 2-4 weeks.
For off-site backups. I use Syncthing and it is running on a server at a families house. Few miles away.
I picked Syncthing over ZFS because I actually a little more than an off-site I wanted a two way sync between our two locations so both locations could have a local copy they can edit and change.