My configuration:
nxdomain.info. 600 IN A XXX.XXX.XXX.XXX
nxdomain.info. 600 IN AAAA XXX:XXX:XXX:XXX
*.nxdomain.info. 600 IN CNAME nxdomain.info.
nxdomain.info. 86400 IN HTTPS 1 . alpn="h3,h2"
Querying the HTTPS RR via apex works:
https://dns.google/query?name=nxdomain.info&rr_type=HTTPS
I can also successfully query the A/AAAA records of any subdomain via CNAME:
https://dns.google/query?name=something.nxdomain.info&rr_type=A
https://dns.google/query?name=something.nxdomain.info&rr_type=AAAA
The HTTPS record can’t be queried via subdomain though:
https://dns.google/query?name=something.nxdomain.info&rr_type=HTTPS