Epic Games has ceased providing Custom Matchmaking Keys for community-run Competitive Fortnite Events. At the time of writing it seems that this does not affect players outside of France.
Kimundi, Community Manager at FortniteFR had this to say on Twitter (translated):
Following an internal decision, it was decided that access to custom games would no longer be given for competitive online events until further notice. Tournaments already validated are maintained.
The “funs” and offline tournaments are always eligible, either through direct contact or through our form.
I recall that these accesses are a quasi-exclusive privilege to the Francophone community. We need to adapt to the internal rules so as not to jeopardize the future projects of our teams.
It appears this suspension is indefinite for the time-being. Perhaps there are bigger plans in the works which are yet to be announced, stay tuned.