I am unable to "Preview" a Template in the Web Client in LF12 and in the Desktop client, although I can preview it, it does not show the layout that I have designed, which I would expect since it does not have the new layout functionality.
I have provided screenshots below of the Web Client preview in the template list (Image A) and from inside the template (Image B). Both show nothing. This is my experience whether working with a newly created template or one that was created before updating to LF12.
Image A
Image B