I think this is it https://lnp2pbot.com/
It's peer to peer, but not trustless. There's a moment in the transaction at which one party can default. So they need a reputation and dispute resolution system.[1]
You'd think there would be trustless decentralized exchanges by now. Ones have been proposed.[2] Some even exist. It's possible to have a truly trustless exchange where orders are smart contracts on a blockchain, transactions are atomic swaps, and at no moment does a third party have custody of anything. This is called an "on-chain order book". It's rarely seen, because it's slow, lacks liquidity providers, and is subject to front-running. Also, nobody makes a billion dollars running one. Most so-called "decentralized exchanges" turn out not to be totally trustless inside.
[1] https://lnp2pbot.com/learn/common-problems-and-solutions.htm...
[2] https://www.smartcontractresearch.org/t/research-summary-tex...
This concept applies to custody, not to fiat-to-crypto exchanges. Because a fiat-to-crypto exchange is an on/off ramp into/outside crypto. And as fiat cannot be held in a trustless way, the most "trustless" way to make a swap without the exchange holding the fiat amount is by using an escrow system. If the escrow system can only be moved to party A or party B during a trade-dispute, then it's the most trustless thing you can get, my friend.
PS: Your 2nd link seems to suggest that you're saying "DEXes are better than p2p exchanges!", well, DEXes don't have fiat-to-crypto pairs, only crypto-to-crypto. Nice try.
Irrationality, Extortion, or Trusted Third-parties: Why it is Impossible to Buy and Sell Physical Goods Securely on the Blockchain