If The Crossing was cancelled, it must have been mostly because it has already been finished. Its ending doesn't feel hastened or partial, I don't see why it would ever need another season.

Leftovers looks interesting but not similar. In the Crossing, the new people actually appear of nowhere and below the sea. First, they are considered survivors from a Russian research vessel, but they speak fluent English and talk about the future. You can check it, it doesn't feel unfinished at all.

I don't know if the school drama of Locke and Key is part of the book. But it feels like it could be. The only part is that them going normally to school and then playing with magic keys doesn't come together when I think about it.

Thanks for a link.