Hardware USB Controllers?

[Samie]

Will the USB NES/SNES/N64 controllers work on a Wii U?

Specifically if I'm playing virtual content? (all sorts of retro games via injection/eshop)

And if so, is it just plug and play? Or anything special I need to do?

 

[AkikoKumagara]

If you're running homebrew, you'll want to check out HID to VPAD. It will enable support for all kinds of gamepads, and if the one you want to use isn't already supported, you can easily add support for it yourself.
https://gbatemp.net/threads/hid-to-vpad.424127/

More info on supported gamepads as well as how to add your own can be found here:
https://github.com/Maschell/controller_patcher_configs