Azure Stack HCI AKS also means AKS Hybrid, doesn't have a native backup solution. When you search about backup solution for this product you will find only Velero Backup Solution in Azure Docs. [Backup AKS Hybrid With Velero][1]
AKS hybrid uses akshci CSI drivers and this driver doesn't support Snapshot resource and all other well known backup products use snapshot resources for backup of Kubernetes CRDs.