@cayce I don't know about your clone but I have an official Wii U controller and it is definitely Bluetooth. It is an odd version of Bluetooth though like the Wiimote. I have no experience of making it work on my Pi4 but on a Windows PC they require some fiddling/extra drivers. I've been using a Wii U Pro controller for CEMU on my PC.
I understand that they can be used as a wiimote (wiimote and nunchuck?) and I would like to look into using it as such when 64bit Retropie/Dolphin comes around. That will be some time off though.