In Belgium these are not banned because of a pure ban on loot boxes, but because of a law that defines illegal games of chance.
This law has been in effect for years and years, and recently the Gaming Commission has made it crystal clear (after an in-depth analysis of multiple video games and their monetisation tactics) that loot boxes are in fact an illegal game a chance. There is no skill involved in the item you're getting: it's purely chance. Exactly this mechanic defines it as an illegal game of chance, as there is no license given for this game of chance to be implemented in these video games. In Belgium, it's very heavily regulated which games of chance can be operated and where. The Gaming Commission has a website with more info, for those interested:
https://www.gamingcommission.be/opencms/opencms/jhksweb_en/law/.
Nintendo implied in their messaging about the shutdown of these games that they are doing this because of "the unclear situation regarding the law on loot boxes", but it's interesting to know that the Minister of Justice has already given media the response that it's very clear: without the loot boxes, the games are perfectly fine to operate and monetise.
So to summarise: you can of course monetise your game in Belgium, as long as what it is exactly that players are buying is not left up to chance. So if I'd want to buy those new Fairy Wings, I would be allowed to spend $100 or even $1000 on it if that is what Nintendo charges. But Nintendo is not allowed to get me to buy 20 Fortune Cookies (even if they cost only $1 each) and still not get a single Fairy Wings set. And we all know this has happened to many players before