opnsense.admin.forth.gr has no CNAME records.
Question and response
Question
dig opnsense.admin.forth.gr. NS
Answer
The response has no answer records.
Authority
admin.forth.gr. 6192 SOA dns1.ics.forth.gr. noc.ics.forth.gr. 2022112803 21600 7200 3600000 172800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0