After you upgraded or migrated all vCloud Director servers and the shared database, you can upgrade the NSX Manager instances that provide network services to your cloud. After that, you can upgrade the ESXi hosts and the vCenter Server instances that are registered to your vCloud Director installation.
Starting with version 9.7, vCloud Director supports only advanced edge gateways. You must convert any legacy non-advanced edge gateway to an advanced gateway. See https://kb.vmware.com/kb/66767.