I wouldn’t lump Github with Facebook or Twitter because, at its core, it’s just a plain jane git server. If you stick to core features, you can exfiltrate your repos at any time in seconds and move them someplace else. And you can interact with Github’s git server with open-source, fully documented tools.
It’s the extended features Github offers that lock you in - the social media stuff and advanced git tools. So if you want to give Microsoft the finger, use Github only for basic services.
Me, I host all my repos there, and I use them also to host videos and as Linux distro repositories (apt and rpm) for my packages: I make it my duty to use up as many Microsoft resources as possible without paying them a dime and without giving them any edge to lock me in.
It’s worth noting that this forum is an attempt to collect cases where essential public interaction is forced into a walled garden. It’s perhaps rare that a government would force the general public to connect to MS Github. I should probably clarify that on the sidebar.
It’s also worth noting that the EU has a public git instance which they self-host. So it implies that there is a reasonable chance that a gov would push Github onto people.
(update: just noticed the FCC exposes the public to Github)