I could buy a couple of used Living Whites plugs, so I would be interested if someone succeeded adding them to ST?
If they can’t be added to ST the normal way, I would attempt to manually create the device and use the generic “ZigBee Dimmer” device type. Instructions on how to add a device manually can be found here (instructions for Xiaomi, but it’s the same for any ZigBee device, of course).
To clarify: I would pair the plugs with my Hue v2 bridge instead of the ST hub because all my lights are there as well, but I’d like the possibility to move them over to SmartThings should the need arise.