> Where do you keep Issues, Pull Requests, Wikis, Discussions, project boards, and everything else? (rhetorical question.)

I think it's worthy of a non-rhetorical answer anyways: https://docs.gitlab.com/user/project/import/github/#imported...

None of those might be perfect, but at least people are trying. Even something like Gitea and other forges that you can host yourself have support for most of the basic functionality you'd expect.

However, If we ever wanted a setup where it's easy to mirror rather than import stuff, we'd probably want to look in the direction of storing everything in folders within the repo, e.g. a file/folder for every issue, for every Wiki page etc. Most of the mirroring seems to only concern the repo itself, not the stuff around it, for example: https://docs.gitlab.com/user/project/repository/mirror/