Luckily DuelBits have an ANN on the Bitcointalk forum, it will be much troubling if this casino is one of those that are not available on the forum, this is why choosing from the list of online casinos on here is the best.

I don't want to believe that this problem is unsolvable, I have made such mistake with a few crypto exchanges before and only two helped when I contacted them through telegram channel, but I was forced to pass KYC verification first, and the amount is not even that much, around 196$ at the time, they refund the money and told me to never repeat such mistake again.

On the Huobi exchange, I made the same mistake, This exchange has a limit point of deposit for every asset available on the exchange, so I deposited below that amount and the fund never reached my account, I contacted them and they said there is nothing they can do about it.

Huobi is considered a big crypto exchange, yet they can't help me out, I think this is a form of punishment for those who lack patience when operating any platform, I learned from my mistake but honestly, they should be able to help.

I hope the same thing won't happen with this OP's case, your best shot is to drop this issue on their ANN and wait for a reply, all the best.

The only thing duelbits can do is send your USDT-TRC20 back to your address because they only have USDT options on ERC20 and BEP20.
But unfortunately, I doubt they will do it to return your deposit because there are many cases like this, and every time you make a deposit there is a warning about what will happen if you make a mistake to the deposit.
https://www.talkimg.com/images/2023/09/06/mTY9g.png
Sorry for your loss, it's not a small amount of money and it's hard to accept this loss, but it's a lesson to be more careful, always double-check before pressing the send button.
However, if in the end Duelbits is willing to send your money back, that should be appreciated.