The only way to backup your data from on-prem ONTAP to on-prem StorageGRID (using SnapMirror Cloud technology) without any additional licensing costs is by using the System Manager as the orchestrator. This went under the radar but it is possible (and supported) since ONTAP 9.9.1: https://docs.netapp.com/us-en/ontap/task_dp_back_up_to_cloud.html
Yes, you need a "SnapMirror Cloud API key" (which should not be mixed up with the "SnapMirror Cloud license") but you get that for free from NetApp.
But this is really rudimentary, you can simply backup the volume and that's about it. No object-locking, no archiving tiers, no index so no searching, no single-file restore. And officially you can only restore to the original source-cluster.
(Actually single-file restore is possible via CLI but very complex and not supported.)
I think we only have one customer who does that because only a simple backup is needed to another medium (non-ONTAP) and the StorageGRID was already available.