Updating a single node cluster is similar to updating a stand-alone node as a Cluster Aware Updating process cannot be used for a single node cluster. A Cluster Aware Updating process involves pausing a node and moving the physical drives into storage maintenance mode. This is not supported on a single node cluster.
Single node clusters must be updated from Server Manager view in Windows Admin Center. Operating system and hardware updates must be made independently and are not supported in the same workflow. Single node clusters cannot be paused or moved into Maintenance Mode, as there are no secondary nodes in the cluster to live-migrate the workloads.