

Except it isn’t. Saying it is trivial is just gross generalization. It’s trivial to configure bind to have internal zones that aren’t resolvable publically. It all depends on configuration, such as reverse ns entries, zone accessibility, etc.
You can have (sub)domains that are listed in the certificate lists and yet aren’t resolvable externally as well.






Absolutely. Simply use ACME with the DNS validation method. Using bind you’ll want to create keys and allow TXT access for those keys to the validation domains. Fear not, this isn’t exclusive to bind, ACME tools supports dozens of other backends. That’s all you need the actual domain doesn’t need to be resolvable with an A/CNAME record. Internally you can run an entirely different DNS server to resolve your hosts, use hosts files, or use bind zones.