OP this is a very good topic but maybe you should add exact License information for each casino, and I know that most of them are using one of Curacao licenses but some use different.
One example I know is BTC365 website that is using E-Gambling Montenegro gambling license, but there are others who use license from Costa Rica.
I haven't checked BTC365 yet. But all of the listed casinos are operating with Curacao gambling license (except Blackjack.fun). However, they are working on it and they said it will be available within this month. You will find that every casino is operating with one of those 4 master license providers of Curacao. I believe it isn't hard to find out the details as I have already added some information about the 4 master license operators in the post. But I will keep your suggestion if I find any popular crypto casino with other license providers without Curacao gambling providers.
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There is no way for a casino to prevent those underage players. Although, it will be possible if a casino makes the KYC (identity documents verification) requirements mandatory during sign-up.