When attempting to delete NSX-T there will be an error message that it is still tied to a Provider VDC. While the network pools and edges have been cleaned up we're unable to remove NSX-T from a Provider VDC in Cloud Director without creating a new Provider VDC.
VMware Cloud Director 10.6.x
Open a support request with Broadcom VCF support. Provide the logs following the KB article here: https://knowledge.broadcom.com/external/article?legacyId=1026312. Provide a backup following: https://techdocs.broadcom.com/us/en/vmware-cis/cloud-director/vmware-cloud-director/10-6/vmware-cloud-director-installation-and-upgrade-guide-10-6/deployment-uprade-and-administration-of-the-vcd-appliance-install/vcd-appliance-administration-install/backup-and-restore-of-your-vcd-appliance-install.html.