The problem is that most active platforms only offer trading of "tokens" and "pegged tokens". Atomic swaps are supported only by few of them. I've made a list in German. To resume: AFAIK at the moment only BarterDEX and Blocknet offer working graphical tools to realize atomic swaps. BarterDEX already works for a year or so, and also Blocknet has published its open Block DX tool, although Blocknet requires additionally a Blocknet cryptocurrency client, so there is more hassle involved.

Bisq is an alternative: For altcoin-to-altcoin trading there is almost no risk, as it's easy for the arbitrators to prove that one of the parties scammed the other. And it offers fiat-to-crypto trades, albeit it's more risky.

Edit: Just checked Blocknet, seems to be active.