They use Plone 6

Websites built with Plone 6

Using Volto as default frontend.

Open-source websites built with Volto

The following websites have been built with Volto. You can find their complete source code by following their links. Please note that complex websites are built on top of Volto add-ons, and most of the time they're just an empty shell for the add-ons. You should check the dependencies in their package.json for more details.