Git doesn’t have a concept of a preferred repository; your local copy is exactly as valid to git as a git server hosted on github.
The originally intended workflow as I understand it involved generating patches which would be shared via a mailing list.
In practice there will generally be a repository that’s considered “canonical” for a project, whether that’s the one on the computer of the lead maintainer or some hosted solution.
A basic git server is essentially just a repository owned by a restricted user with SSH access granted to maintainers.. This can allow users to push and pull from a centralised or semi-centralised repository in much the same way as GitHub.
They deliberately removed code search for not logged in users almost immediately. Just recently they removed cloning without an account, so now updating my computer requires signing in to github.
They have been awful stewards.