Currently, my answer is Changelly Pro. It's quite modern and has a number of helpful trading features. Recommend to try.
How about another little-known and not-so-popular cryptocurrency trading platform? Is this the first time you've heard about Paxful? You can read a little about it here -
https://cryptototem.com/paxful-review/. I can’t imagine the reasons that might induce the use of such small exchanges. Tell me, for what reasons can you change giants like Binance, Kucoin, Bittrex for similar little-known trading platforms?