Both scenarios I was referring to are on GCP, but one is on k8s (GKE) and one uses ordinary GCP VMs. In both cases we're using the multi-reader mounting feature of GCP persistent disks, all that changes is how that's specified.

Outside GCP, we do have an on-premise product that can deploy on any k8s cluster. In that case, the default is for the customer to provide an NFS mount for the data in question. We use the same k8s ReadOnlyMany access type for that.