Any idea where this went? I can’t reach https://forum.openstreetmap.fr/
It’s back online. Thanks @Jocelyn I suppose ! 
Yes, it is just back online 
There are some explanations here: Back to the future : forum restauré! - Annonces - Forum OSM France . We had some problems during a discourse update, and had to revert back to an (slightly) earlier version of the forum.