bisq is the closest I know

But I was imagining something clever with bisq

bisq is all about independent escrow and being able to buy and sell from anyone on the planet with some measure of distributed trust

Now imagine applying that same technique to a stablecoin

In order to redeem it you redeem it directly with anyone who's currently part of the network

In order to mint it somebody locks up dollars in escrow

no centralization

Now you can create a lightning atomic swap exchange

so you have a real time decentralized market, solving the true problem of onboarding in Bitcoin

checkpoints on the main chain to maintain a consistent state

I think at this point it's totally possible and just nobody's sat down and done it