What about AgoraDesk? It supports Monero but I am not sure of it's decentralized nature. They have an arbitration feature but I don't know much about it. LocalMonero is basically the same thing with a different name. 
Isn't UnstoppableSwap a decentralized solution for Monero?
Also, Robosats supports Monero. I think it's still centralized, but there was a proposal to make it decentralized. No idea how far they have come with that. If I remember correctly, there was talk about the decentralized solution becoming custodial during trades, so that's not optimal.