When you try to create a second supervisor cluster on an existing ESXi cluster you see "Cluster with identifier domain-xx already has Workloads enabled." under "Incompatibility Reason"
vSphere Kubernetes Services
This is expected behavior supervisor clusters cannot share an ESXi cluster
This is expected behavior
for more information on supervisor cluster deployments see below:
https://techdocs.broadcom.com/us/en/vmware-cis/vsphere/vsphere-supervisor/8-0/vsphere-supervisor-concepts-and-planning/vsphere-with-tanzu-deployment-options/supervisor-high-availability-and-single-cluster-deployments.html
https://techdocs.broadcom.com/us/en/vmware-cis/vsphere/vsphere-supervisor/8-0/vsphere-supervisor-concepts-and-planning/requirements-for-enabling-a-single-cluster-supervisor/requirements-for-cluster-supervisor-deployment-with-nsx.html