I'm a UBports contributor, so i might be biased, but i think it would be great if new questions about Ubuntu Touch could still be accepted. Yes, Canonical is no longer maintaining Ubuntu Touch, but it's still very much alive in the community, and there's no reason that should change any time soon. ;)
Ubuntu is not only about Canonical, so I think the policy should not be that everything that Canonical doesn't directly support is off-topic.
If Ubuntu Touch questions will be accepted here in the future, we would definitely advertise it more actively to Ubuntu Touch users again.
One thing that the moderators and reviewers should pay attention to is that the Ubuntu Touch tag should only used for questions that are actually about Ubuntu Touch, not questions about using other Ubuntu flavors with a touch-screen.