2020-03-25 It's 2020 and github doesn't support IP version 6
Several of the machines here at home have IPv4 to the outside world disabled, simply to find every ancient service or program that still lives in the old world. Today I found one of those while installing dehydrated to automatically renew Let's Encrypt certificates. Indeed, github has no IPv6 support. It tries to be a modern service, but lacks an AAAA record. The solution is simple: use a webproxy to solve this. The only reason I still have a squid webproxy running is to be able to access IPv4-only http/https services from those hosts, so setting the http proxy in the global git config helped. I'm just surprised github doesn't support IPv6. Update: After some searching I found Github users have been asking about IPv6 connectivity since at least 2018 and the "solution" is that they currently don't support IPv6 and the request is on some list.