Looks like you will have to join the NVAV (
https://www.nvav.nl/home). You will have to have a chat with them to see if these kits can be built and flown here. Joining other associations such as the LAA or the EAA might certainly be worthwhile as they will have more experience with these types. Best thing to do in my view is find someone who will let you have a close up look at the type, perhaps even fly it, so that you can see if that is really what you're looking for. Discuss problems that cropped up during the build, etc.
Edit: on PPRuNe, you might consider asking this question in the Private Flying forum.