@box said:

If you are seeing border geometry it usually means there is a hole or your shape has no thickness.
A solid has to be a manifold shell of faces, a watertight container, otherwise it is just a mesh.
There are other basics about solids but without seeing what you have it is all guesses.

That must be it - no thickness to my mesh - thanks 😄

You can't select a different template for specific pages but you could open a second LayOut project using your other template and copy the content from one project page to the other project. Keep in mind that when you paste the content into the project, all of it will be placed on the active layer for that project. If your template file has content on multiple layers, you'll either compress it all to a single layer when pasting or you'll have to copy and paste content one layer at a time.

An alternative would be to just make two separate LO files, one for the front page and one for the other pages and combine them in Acrobat or some other PDF editor.