In this year 2025, the main GitHub domain still doesn't serve over IPv6.
Some subdomains do have IPv6 though, just... not what you would expect.
For instance, avatars.githubusercontent.com:
; <<>> DiG 9.18.28-1~deb12u2-Debian <<>> AAAA avatars.githubusercontent.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 18015
;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;avatars.githubusercontent.com. IN AAAA
;; ANSWER SECTION:
avatars.githubusercontent.com. 159 IN AAAA 2606:50c0:8002::154
avatars.githubusercontent.com. 159 IN AAAA 2606:50c0:8001::154
avatars.githubusercontent.com. 159 IN AAAA 2606:50c0:8003::154
avatars.githubusercontent.com. 159 IN AAAA 2606:50c0:8000::154
;; Query time: 32 msec
;; SERVER: 2a09::#53(2a09::) (UDP)
;; WHEN: Wed Jan 08 04:55:56 UTC 2025
;; MSG SIZE rcvd: 170
Whereas none of the other domains accessed when accessing github.com (named github.com, github.githubassets.com and alive.github.com) has IPv6.
The package registry ghcr.io as well doesn't support IPv6:
; <<>> DiG 9.18.28-1~deb12u2-Debian <<>> AAAA ghcr.io
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 967
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
; EDE: 29: (Result from negative cache)
;; QUESTION SECTION:
;ghcr.io. IN AAAA
;; AUTHORITY SECTION:
ghcr.io. 547 IN SOA ns-773.awsdns-32.net. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
;; Query time: 32 msec
;; SERVER: 2a09::#53(2a09::) (UDP)
;; WHEN: Wed Jan 08 04:57:35 UTC 2025
;; MSG SIZE rcvd: 152
And so does gist:
; <<>> DiG 9.18.28-1~deb12u2-Debian <<>> AAAA gist.github.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 52139
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;gist.github.com. IN AAAA
;; ANSWER SECTION:
gist.github.com. 1019 IN CNAME github.com.
;; AUTHORITY SECTION:
github.com. 182 IN SOA dns1.p08.nsone.net. hostmaster.nsone.net. 1656468023 43200 7200 1209600 3600
;; Query time: 32 msec
;; SERVER: 2a09::#53(2a09::) (UDP)
;; WHEN: Wed Jan 08 04:58:11 UTC 2025
;; MSG SIZE rcvd: 123
So yeah, years later, always the same excuse, and no support at all.