Syncthing
Syncthing is generally not a backup tool. But as we use snapshots on the ZFS pool, which can't be destroyed from syncthing, it's not a plain syncing tool which in the worst case would sync ransomware encrypted files in real time and cause data loss on all devices.
The Syncthing GUI will be available through the provided link after deployment.
To prefill the Syncthing dataset on your ZFS pool before sending it, install as described in Install Syncthing. You don't need to do this if you don't want to prefill the pool on your site.