Apex domains cannot have CNAME records.
Question and response
Question
dig linkage.net. NS
Answer
linkage.net. 5 NS ns1.hk.net.
linkage.net. 5 NS ns2.hk.net.
linkage.net. 5 NS ns11.hk.net.
linkage.net. 5 NS ns12.hk.net.
Authority
The response has no authority records.
Additional
ns1.hk.net. 5 A 152.101.179.98
ns2.hk.net. 5 A 152.101.179.102
ns11.hk.net. 5 A 152.101.25.14
ns12.hk.net. 5 A 152.101.4.18
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0