You need to create GLUE records for your Virtualmin Server IP at your registrar.,
If your server has for example hostname.domain.tld set the glue record to that with the IP. Also add ns2.domain.tld for example you can have the IPs be the same.
And then set domain to use those nameservers, you glued.
In virtualmin have NS records and also A records for the ns names you chose.
GLUE Records? I’m sorry that’s unfamiliar to me, because I’m new in DNS World.
Can you tell me how to create that Glue Records for my Virtualmin Server?
Btw, when i test with nslookup inside that server, all queries are replied: