They are officially listed by Chia on their website and are open source via GitHub
Chia with their offer system is quite unique and is a step up when it comes to anything DEX related.
TibetSwap adds another option to invest your XCH (by adding liquidity). But do your own research as there is always an element of risk. TibetSwap does a nice job explaining the risk factors.
I like where Chia is going…