A couple of months ago I was testing WebApp Builder and noticed that in BasemapGallery widget there is no support for WMS-basemap.
But now for us more crucial is WMTS service support.
I have any luck having our http://tiles.maaamet.ee/tm/wmts? as a basemap there. So, the question is - will WebApp Builder support WMTS in the future? Or is it present in 10.3 already?
Estonian Land Board