Hi,
I had the same issue as you. Have one “dumb” lamp, which I can’t put a smart bulb in, and would like to be able to move it around (and be able to dim the light).
So I was searching for simple smart plugs with dimmable feature and ZigBee/Z-wave connection, to be able to include it to my Smartthings Hub V3. Found this Nexa Plug, and added it as instructed, but wondered like you why it connected as an Evergreen remote, so I started shuffling around with the different IDE, and looked for any possible custom device handlers… That’s when I found your post, and assigned the standard Z-wave dimmer switch IDE. Now I am also able to control it from the Classic Smartthings App, but stuck with the “checking status” message in the new app.
My workaround has been to create a Virtual Dimmer Switch, and simply configure the Nexa plug to mirror it through the Smart Light Smartapp in the Classic ST app (perhaps it could be configured through the new ST app as well).
And now I am able to switch on/off and dim the light through the new app, using the Virtual Dimmer Switch, which I have renamed the Lamp name originally planned, and moved to the room in the dashboard overview, and just hid the Original Nexa tile.
Don’t know of there is a better way to do this, but it works for me, for that one Dumb lamp 