Marker-based AR in Wonderland Engine

Is there a marker-ed AR solution that has been tried with WLE before?

Yes, you can use 8thwall, if their pricing model works for you.
(Update 02/2022: We now also have an integration with mind-ar-js, see GitHub - WonderlandEngine/wonderland-mind-ar-tracking: Wonderland Engine integration of mind-ar-js image and face tracking)