I am not sure whether this is Virtualmin issue or just Webmin (but since install.sh installed everything, I am reporting it here) just FYI
I tried to "Apply Zone" (Webmin-> Bind DNS Server section) and get the following error:
NDC command failed : rndc: /etc/bind/rndc.conf does not exist
That file doesn't exist indeed. Restarting Bind works fine, but doesn't help. Apply Configuration works as well.