Unfortunately, I don't have much experience on dark web, so I haven't heard about this exchange. If it's not secret, can you tell why do you need to use dark web exchange? My only advice would be - you should be extremely careful while dealing there. Dark web is full of scams and zero protection from them.
Some people do engage only due to some sort of curiosity and majority doesnt even know on what are the things that lying ahead when it comes to risk on being scammed nor being imprisoned/caught on dealing mostly with illegal things into that place.
About on the question about that UBOT.I havent heard out such thing and also same as you said its better not to deal with things which arent even known specially to these shady places.
Why would care if there are legal and known ones?
? I was told by some one to look for this exchange. Obviously its not available on normal internet. Like onion sites this exchange also be accessible by some special browser of proxy.