I just saw this on Blackjack.fun's
special no-deposit campaign, is KYC mandatory in this casino?
5. To prevent abuse and ensure a fair gaming environment, users must complete KYC (Know Your Customer) verification before participating.
No. KYC is not mandatory but just like other casino, they may ask you randomly. The promotion that you mention is their way to attract new user to undergo KYC just to get the bonus reward.
I still have my account not verified until now but I rarely play on this casino these days so maybe this is the reason why my account is still not ask to KYC even if my account age is old enough.