There seems to be no such thing as a "private fork" on GitHub in 2024 [1]:
> A fork is a new repository that shares code and visibility settings with the upstream repository. All forks of public repositories are public. You cannot change the visibility of a fork.
> A fork is a new repository that shares code and visibility settings with the upstream repository. All forks of public repositories are public. You cannot change the visibility of a fork.
[1] https://docs.github.com/en/pull-requests/collaborating-with-...