During NSXT decommission process for a NSX cluster prepared only for Security, 3 NSX distributed port groups configured on NSX segments could not be removed manually.
The delete option for these distributed port groups were "grayed out".
NSXT 3.2.2
TCP 2.2
The NSX-T cluster was prepared by the system for Security only. So the distributed port groups couldn't be manually deleted from NSX GUI or from API
Remove the transport node profile attached with the cluster. After the transport node profile is removed from the cluster, the NSX distributed port groups should get deleted automatically.
If the issue still persists contact Broadcom support Creating and managing Broadcom cases