`ManagedClusterSet` is not currently documented in the API https://access.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes/2.8/html-single/apis/index#rhacm-docs_apis_clusterset_jsonclusterset

It is documented upstream https://open-cluster-management.io/concepts/managedclusterset/ however ACM 2.8/MCE 2.3 do not support all of the same specifications.

ACM does not support setting `selectorType: LabelSelector` as shown in the example below from the upstream documentation. This limitation should be clearly documented in ACM.

apiVersion: cluster.open-cluster-management.io/v1beta2
kind: ManagedClusterSet
metadata: 
  name: example-openshift-clusterset
spec: 
  clusterSelector: 
    labelSelector: 
      matchLabels: 
        vendor: OpenShift
    selectorType: LabelSelector