Sellix.io was really easy to use for me, and I'm not a dev. It allowed us to take various forms of payment all from one place. We could do various crypto, Cash App, PayPal, Venmo, and fiat all from one location. It also gave us the ability to create coupons for users. That's how we handled bookers' licenses and also the new account creation with join.woo.game, but now that is also down.
It's unfortunate, and even Stripe heavily promoted Sellix on their main page, so it had a good reputation. I guess they, as a company, should have looked into the items being sold through their service, but it is what it is. To be honest, I'm sure Discord shops are places where a lot of potentially harmful pieces of software are also sold, but I'm sure cyber-criminals preferred the ability to accept crypto as a form of payment for the anonymity that it can provide. I find it interesting that they seized crypto. I'm guessing keys were stored on the phones or devices that were seized. It seems pretty unsecure to me if a government agency can just seize your crypto.