If you're considering moving away from github due to problems with reliability/outages, then any migration to gitlab will not make you happy.

> If there's a way to import issues and projects I could be sold.

That is what that feature does. It imports issues and code and more (not sure about "projects", don't use that feature on Github).

Maybe it's be reasonable to script using the glab and gh clis? I've never tried anything like that, but I regularly use the glab cli and it's pretty comprehensive.