Exporting Layer Groups As Pages Within A PDF Doc

[tamj]

I use GIMP 2.10.18.
I want to export an .xcf file project (for a brochure) so that the content in each layer group is combined onto a single PDF page. That way the entire project will become a multi-page PDF document ready for download and printing from a commercial website.

Using the current functionalities I can only export to a PDF with only the topmost layer-group shown on it.
On GIMP I can hide the topmost layer-group content and then I see the page underneath shown on the main GIMP window. But whenever I try exporting that single page to PDF, all I get is a PDF with the topmost page alone in it.

How should I configure things so that I can get each layer-group to become a single page in a PDF file ?

[Ofnuts]

I have a script to flatten groups to a single layer, that you could run before exporting: flatten-groups-0.0.py