Trying to find a 20 amp outlet but community posts are a bit dated on this topic. One on Legrand seems to work but will require additional bridge. Anything out there that works natively with ST?
Swidgit has a 20 amp zwave option, but it’s super expensive, a quirky design, and reviews are that customer service is nonexistent. Personally, I’d definitely choose Legrand instead, but for completeness, here it is:
You have to get the Zwave version which right now only seems to be available from their own website. Then it should just show up as a basic on/off switch.
I definitely wouldn’t get any of the various sensor add-ons, though, they aren’t going to work with SmartThings. But viewed just as a 20 amp outlet, it exists. But like I said, it wouldn’t be my choice. 
I keep hoping we’ll see a 20 amp matter outlet from somebody eventually, but I haven’t seen one yet.
(Three of the older models, from Currant, ConnectSense, and TopGreener have all come and gone over the last 10 years. I’m not sure why this particular device class seems to be challenging, but obviously it is or we’d see more of them. Right now Legrand pretty much owns the category.)