But gitlab has a Github migrator which supports pretty much a repos complete history (PRs, issues, wikis, etc).
Yup, I am aware of that thanks to my obsessive reading of HN :-) But I was just pointing out that it's not easy as switching a git origin in case you want to move to something else other than GitLab.
A pain point here is that GH issues cannot be migrated easily as a git migration (but GH does have a REST api).