"Unexpected Error. Contact Citrix Support" while trying to select a cluster when adding a SCVMM hosting connection:
Update the scope of the account used to configure the hosting connection to have access to only one single top level host group.
Multiple top level host groups are currently not support with SCVMM hosting connections.
Note : With Citrix Virtual Apps and Desktops 2212, you can limit host group scope used in SCVMM hosting connection. In order to do so, please refer this - https://docs.citrix.com/en-us/citrix-virtual-apps-desktops/2212/whats-new.html#limit-host-groups-scope-in-scvmm-host-connection