I leave this here for future reference. Since the Plugwise Plug is quite a good smart plug (energylevel meter, maximum Amps/Wattage supported, cheaper than Fibaro etc).
I recently connected my Plugwise Plug to my Adam. Adam supports this now. Before you only could connect Plug to the P1 Smile.
When I tried to connect the Plug via the Homey Plugwise app (NOT the Plugwise Zigbee support app).The Homey app found the Adam. But I could not get the Plug to show up in the device-to-add list.
Turns out, I looked at the sourcecode, you need to specify the Appliciance Type for the plug in the Plugwise IOS/Android app. It needs to be set to Miscellaneous.
I created a patch to fix this, hopefully Athom will accept it. Untill then, setting the Appliance type to Misc is the workaround.