Driving in France - child seat belt requirements in a campervan

I think this is a simple question but can’t find the answer anywhere or anywhere to ask.

I have a converted VW transporter which has 3 factory fitter seats (and seat belts in the front).

The back is an aftermarket campervan conversion which includes 2 seats in the back with seat belts. However these are not M1 tested or MOT tested.

Can my 4 year old travel in the front of the van in France?

https://www.lolivier.fr/regles-transport-enfant-en-voiture.html