Currently, AU only has a defined migration path to Meta:
Why is there no migration paths defined for U&L SE, and possible the ElementaryOS SE as well? To me, it would make more sense to be able to vote for moving than closing questions related to non-official derivatives of Ubuntu - and I believe it would benefit the users as well.
As it is we have to advise users to delete the question on AU and re-post on the appropriate site. Moving would offer a better exprience, especially to new users of both AU/SE and Linux.