The current LibreOffice extensions and templates website runs with custom Plone ATContent-Types. The ATContent-Types were the default content types for Plone up to version 4.3.x. The new Plone 5.x versions uses the new Dexterity content types as default. The new LibreOffice extensions and template website will also use (customized) Dexterity content types. Thus the content from the current website has to be converted to the new framework. I currently investigate a simple and easy way to do this conversion.
I got already a local copy of the site content running with a newer Plone 4.x version and will investigate the further steps to map the types and fields from the current content types to the new ones.