Maybe you already tried but, try to talk to the customer support team of that services and see if they can do a CPFP as I see that RBF is not enabled on that tx.
I would be very surprised if that worked, but it doesn't hurt to try. I am yet to meet a knowledgeable support rep on a crypto casino that has something more than a very basic understanding of how Bitcoin and crypto works. It would require Gamdom to play around with private keys, which they might not be happy about. It's hard to get centralized exchanges to do it for the same reason. And the question is, can they even do it? They might be working with a custodial service or payment gateway on their end as well.
Yeah I agree is not easy, but to try it, is free, even more if it's their fault because they have miscalculated the fees required. I think how they do is irrelevant, at the end, their service "complexity" should be transparent for the customer.
And another point, if it's not OP fault, if it's company fault I think they MUST do it as they "lost" or "block" their customer money because an error.
Note: I know it's not lost but let's be realistic 6sats/vb without CPFP and RBF and more than 450k tx in the mempool.... An infinite queue on the meempol == lost.