it does not really have to be decentralised but just a platform with gambling games that cannot be influenced by the house.
Lets take paper-scissor-rock as example. 2 persons put for example 1000 satoshi each in the pot and then play the game. The person who wins the game will receive the prize pool of 2000 satoshi (minus the fee that the platform is charging).
So it can be decentralised but can also work like a regular online casino with player accounts where people can deposit some money, receive affiliate income and winnings. I think if you want to make it entirely decentralised you must work with a coin or token that has very fast confirmations. A game paper-scissor-rock for example takes less than 30 seconds to end. So it fast transactions should be necessary.
So I think a platform like a regular casino should work fine with deposit and withdrawals, etc but with exclusively games that can't be manipulated. I think this would be a nice and fair thing if that would be around. Winnings aren't that big cause you do not have the multipliers but you still have a 50% chance to win. Thats even something not a single casino can offer.
This reminds me live casinos. Live roulette, live poker etc which we can usually play against each others. I think there are sites like bet365 can offer you that. But if you are talking about dice and this kind of games then I have not seen any yet or how will this be done?
Not talking about games like on regular casino sites. But just simple games. Lets take another simple game 'connect4' (picture below). This is a very easy game that can be played online. Lets say players put in 500 Satoshi each and winner of the game takes 1000.

You would be able to configure games like dice, mines, etc to multiplayer games but then you still have the risk the house manipulates the game and can favourise house players. But like in games I mentioned like rock-scissor-paper or on top of this connect4 this are real P2P games that can't be manipulated by the house. So everyone has a fair 50% chance of winning