Please realize that there is atomicdex, that does not operate with SCs, but on plain UTXO blockchains, and hence does not have any SC risk.
Atomic Swap is something i have meant to read about but postponed it for a long time now. I admit i don't know anything about yet, so i'll come back after researching to comment something later on. So thanks for the tip. I thought that all of these DEXes would be based on some sort of SC.