Did the above steps and these are my results.
The following name servers are used for lookup of github.com.
;rrset 549 13 1 5 0
com. 549 IN NS i.gtld-servers.net.
com. 549 IN NS c.gtld-servers.net.
com. 549 IN NS d.gtld-servers.net.
com. 549 IN NS f.gtld-servers.net.
com. 549 IN NS l.gtld-servers.net.
com. 549 IN NS k.gtld-servers.net.
com. 549 IN NS m.gtld-servers.net.
com. 549 IN NS a.gtld-servers.net.
com. 549 IN NS g.gtld-servers.net.
com. 549 IN NS h.gtld-servers.net.
com. 549 IN NS j.gtld-servers.net.
com. 549 IN NS e.gtld-servers.net.
com. 549 IN NS b.gtld-servers.net.
com. 549 IN RRSIG NS 8 1 172800 20210516042406 20210509031406 54714 com. rq4GGd+7VBrnTg8dVisKZdVgScFLKdXv8KowpnIcJ0NfTvyHm5i+pmozP58ywXNK8zi4HpvhAcPlp02YWC5IIfUkn4aYpGJHrzGGSc8OGRyMikPIemN0U55GDD6uVHiaO54h1HN96tsTr00htOm2Z4pPUHzitcdWMx8v4LashL4C3SmZAM7symKqvvae0s8W6mDPuvHJAlDL5V27tjemvg== ;{id = 54714}
;rrset 453 1 1 11 4
com. 453 IN DS 30909 8 2 E2D3C916F6DEEAC73294E8268FB5885044A833FC5459588F4A9184CFC41A5766
com. 453 IN RRSIG DS 8 1 86400 20210525050000 20210512040000 14631 . o/c7cxcT52FCuNwXAfz86Rl8WZjWmmEXScBCCe4oa04PpCoJYvipYkee7JWqj9n0GfQF6giHRQpky2D3W+Vv/ntjO375NOlosl4c7oP88Sw3AUHE50gv24aDoWq3D53RpkEzfCsWm/F1LDB40qSx+VkGXY2FiJKJY031B+U3nWwb0lMRFYfckb7KL9mn+A4c6vimle/XTdIOIW3RpEFIfX05rK1Za4cw8qv7p/9SJ+YLI3codzVrpVDOHQmygLMiF2hAx5z2DD9i2Y/ILLxACqDklHSeFN4iyoEGQwFvHEIOxvPBIRPmb8WkjI2W99OIEBMl43fZi0VrI/RL/ZGq6A== ;{id = 14631}
;rrset 549 1 0 5 0
b.gtld-servers.net. 549 IN A 192.33.14.30
;rrset 453 1 0 1 0
b.gtld-servers.net. 453 IN AAAA 2001:503:231d::2:30
;rrset 549 1 0 5 0
e.gtld-servers.net. 549 IN A 192.12.94.30
;rrset 453 1 0 1 0
e.gtld-servers.net. 453 IN AAAA 2001:502:1ca1::30
;rrset 549 1 0 5 0
j.gtld-servers.net. 549 IN A 192.48.79.30
;rrset 453 1 0 1 0
j.gtld-servers.net. 453 IN AAAA 2001:502:7094::30
;rrset 549 1 0 5 0
h.gtld-servers.net. 549 IN A 192.54.112.30
;rrset 453 1 0 1 0
h.gtld-servers.net. 453 IN AAAA 2001:502:8cc::30
;rrset 549 1 0 5 0
g.gtld-servers.net. 549 IN A 192.42.93.30
;rrset 453 1 0 1 0
g.gtld-servers.net. 453 IN AAAA 2001:503:eea3::30
;rrset 549 1 0 5 0
a.gtld-servers.net. 549 IN A 192.5.6.30
;rrset 453 1 0 1 0
a.gtld-servers.net. 453 IN AAAA 2001:503:a83e::2:30
;rrset 549 1 0 5 0
m.gtld-servers.net. 549 IN A 192.55.83.30
;rrset 453 1 0 1 0
m.gtld-servers.net. 453 IN AAAA 2001:501:b1f9::30
;rrset 549 1 0 5 0
k.gtld-servers.net. 549 IN A 192.52.178.30
;rrset 453 1 0 1 0
k.gtld-servers.net. 453 IN AAAA 2001:503:d2d::30
;rrset 549 1 0 5 0
l.gtld-servers.net. 549 IN A 192.41.162.30
;rrset 453 1 0 1 0
l.gtld-servers.net. 453 IN AAAA 2001:500:d937::30
;rrset 549 1 0 5 0
f.gtld-servers.net. 549 IN A 192.35.51.30
;rrset 453 1 0 1 0
f.gtld-servers.net. 453 IN AAAA 2001:503:d414::30
;rrset 549 1 0 5 0
d.gtld-servers.net. 549 IN A 192.31.80.30
;rrset 453 1 0 1 0
d.gtld-servers.net. 453 IN AAAA 2001:500:856e::30
;rrset 549 1 0 5 0
c.gtld-servers.net. 549 IN A 192.26.92.30
;rrset 453 1 0 1 0
c.gtld-servers.net. 453 IN AAAA 2001:503:83eb::30
;rrset 549 1 0 5 0
i.gtld-servers.net. 549 IN A 192.43.172.30
;rrset 453 1 0 1 0
i.gtld-servers.net. 453 IN AAAA 2001:503:39c1::30
Delegation with 13 names, of which 0 can be examined to query further addresses.
It provides 26 IP addresses.
2001:503:39c1::30 not in infra cache.
192.43.172.30 NoAuthButRecursive rto 230 msec, ttl 623, ping 58 var 43 rtt 230, tA 0, tAAAA 0, tother 0, EDNS 0 probed.
2001:503:83eb::30 not in infra cache.
192.26.92.30 NoAuthButRecursive rto 188 msec, ttl 623, ping 48 var 35 rtt 188, tA 0, tAAAA 0, tother 0, EDNS 0 probed.
2001:500:856e::30 not in infra cache.
192.31.80.30 NoAuthButRecursive rto 160 msec, ttl 623, ping 28 var 33 rtt 160, tA 0, tAAAA 0, tother 0, EDNS 0 probed.
2001:503:d414::30 not in infra cache.
192.35.51.30 NoAuthButRecursive rto 150 msec, ttl 623, ping 42 var 27 rtt 150, tA 0, tAAAA 0, tother 0, EDNS 0 probed.
2001:500:d937::30 not in infra cache.
192.41.162.30 NoAuthButRecursive rto 240 msec, ttl 623, ping 56 var 46 rtt 240, tA 0, tAAAA 0, tother 0, EDNS 0 probed.
2001:503:d2d::30 not in infra cache.
192.52.178.30 NoAuthButRecursive rto 226 msec, ttl 623, ping 54 var 43 rtt 226, tA 0, tAAAA 0, tother 0, EDNS 0 probed.
2001:501:b1f9::30 not in infra cache.
192.55.83.30 NoAuthButRecursive rto 145 msec, ttl 623, ping 45 var 25 rtt 145, tA 0, tAAAA 0, tother 0, EDNS 0 probed.
2001:503:a83e::2:30 not in infra cache.
192.5.6.30 NoAuthButRecursive rto 76 msec, ttl 623, ping 32 var 11 rtt 76, tA 0, tAAAA 0, tother 0, EDNS 0 probed.
2001:503:eea3::30 not in infra cache.
192.42.93.30 NoAuthButRecursive rto 184 msec, ttl 623, ping 52 var 33 rtt 184, tA 0, tAAAA 0, tother 0, EDNS 0 probed.
2001:502:8cc::30 not in infra cache.
192.54.112.30 NoAuthButRecursive rto 194 msec, ttl 623, ping 50 var 36 rtt 194, tA 0, tAAAA 0, tother 0, EDNS 0 probed.
2001:502:7094::30 not in infra cache.
192.48.79.30 NoAuthButRecursive rto 500 msec, ttl 623, ping 38 var 53 rtt 250, tA 1, tAAAA 0, tother 0, EDNS 0 probed.
2001:502:1ca1::30 not in infra cache.
192.12.94.30 NoAuthButRecursive rto 157 msec, ttl 623, ping 49 var 27 rtt 157, tA 0, tAAAA 0, tother 0, EDNS 0 probed.
2001:503:231d::2:30 not in infra cache.
192.33.14.30 NoAuthButRecursive rto 137 msec, ttl 623, ping 45 var 23 rtt 137, tA 0, tAAAA 0, tother 0, EDNS 0 probed.
dig +noall +authority @192.55.83.30 ns github.com
nominum.cloud. 199 IN SOA ns4.nominum.net. hostmaster.nominum.com. 2020042997 1200 600 604800 900
dig +noall +answer @ns-520.awsdns-01.net. a github.com
github.com. 600 IN A 74.121.125.9
github.com. 600 IN A 74.121.125.8