https://github.com/openzfs/zfs/commit/b52563034230b35f0562b6...
"The last addition is the ability to do raw, encrypted sends and receives. The idea here is to send raw encrypted and compressed data and receive it exactly as is on a backup system. This means that the dataset on the receiving system is protected using the same user key that is in use on the sending side. By doing so, datasets can be efficiently backed up to an untrusted system without fear of data being compromised."
Unfortunately it's taking a long time for the feature to propagate through the ZFS implementations. I don't know if rsync.net's servers support it.