Use github public keys to authorize ssh connections.
go install github.com/rtgnx/ghkeys/cmd@latest
Allow any valid user from github
AuthorizedKeysCommand /usr/bin/ghkeys %u 2> /tmp/ghkey.log
AuthorizedKeysUser nobody
Allow specific user
AuthorizedKeysCommand /usr/bin/ghkeys --users rtgnx,myfriend %u 2> /tmp/ghkey.log
AuthorizedKeysUser nobody
Users will be looked up against /etc/passwd and check if user id is > 1000