If they have a blog or use a static site generator they could host their github repos online and use a plugin or something to display them. Or even just post links to the repos. It might cause bandwidth issues for popular projects and you wouldn't have any of the "social" features like stars (which in this case would be a feature) but it should be possible. Depending on how the backend is set up you might not even need to put the repos in the web path at all.
But I'd still say just use Codeberg. And see if there's an option to turn off PRs wherever your projects are hosted.
But I'd still say just use Codeberg. And see if there's an option to turn off PRs wherever your projects are hosted.