I got all of my CentOS 8 servers converted to Rocky. First update to the latest CentOS 8 available and reboot. Then make sure the "powertools" is enabled. One last time "yum upgrade" before running the migrate2rocky script and reboot. DirectAdmin didn't even know that anything has changed.
Besides that I installed a few new Rocky servers with DirectAdmin. I didn't find any issues. Just make sure that, for now, you have SecureBoot disabled in your BIOS/VMware. The Rocky people are still waiting to obtain secure boot signing keys.
I wasn't going to wait until the end of the year before finding and testing an alternative for CentOS 8. Rocky is my preferred OS now. There doesn't seem to be a second (commercial) agenda.