I've had good luck using `zfs allow` to grant non-root backup users the ability to only add snapshots to their datasets to avoid the "attacker compromises prod and then jumps to the backup server and deleted the backups". It is an extra step to clean up old snapshots, but worth the risk-reduction.

You can also split administration up so that, e.g., my friend sending me snapshots can't even log in as root on his backup server.