When creating new Virtual Server. Requesting a certificate for domain.com
This issue has been fixed and scheduled for inclusion to Virtualmin 6.11.
I am also getting that error on my new CentOS 8/Nginx server. Somehow, my sites are running okay on it. I don’t know if mail works but that will be for another day. I will wait for the update in 6.11.
You could apply this patch and try again.