I believe there is a documentation inconsistency regarding autolink references between
The feature overview lists that all features are available for public repositories when using the free plan for organizations:
With GitHub Free for organizations, you can work with unlimited collaborators on unlimited public repositories with a full feature set, or unlimited private repositories with a limited feature set.
The documentation for autolink lists only paid options for this feature:
Autolinks are available in repositories with GitHub Pro, GitHub Team, GitHub Enterprise Cloud, and GitHub Enterprise Server. For more information, see “GitHub’s products.”
The autolink feautre is not available for configuration with public repositories, so I guess the more restrictive documentation is correct, but it would be great if you could consolidate this information to clear up the confusion.
Of course, even better / more appricated would be to provide this feature for free plans, too