This is definitely something that could be solved with Stack Exchange moderation tools. Questions could be moved to the appropiate site, the same way you'd move issues between GitHub repositories.
That is already a thing the sites do.
https://duckduckgo.com/?q=site%3Aserverfault.com+%22migrated...
Edit: Eg here's one from June this year: https://serverfault.com/questions/971652/windows-how-to-kill...