So Nintendont was updated to support the GC adapter for Wii U. This is now possible. : r/wiiu

Tutorial: How to use your GameCube Controller Adapter for Wii U on the vWii

Playing GameCube on Wii U - Super Smash Melee (Homebrew) - 2015 : r /smashbros

PSA] I threw together a chart in Paint that lists what controllers will work for Smash 4, as well as compatibility information. : r/smashbros

Nintendont GameCube controller issue - The Independent Video Game Community

Nintendont, Page 2017

pdobq Gamecube Controller Adapter for Nintendo Switch / WII U / PC. Super Smash Bros Switch Gamecube Adapter. 4 in 1 Plug and Play Game Cube Adapter : Video Games

New 2020] How to use Official GC adapter on GC Emulator for WiiU! (nintendon't)

I created a monster, a beutiful monster. Added an “internal SSD to my Wii U as well as Gamecube Ports. And yes it works: : r/ wiiu

Switch to “Wii U” or “PC” mode by using the switch located on the side The GameCube Controller Adapter allows you to connect up to four GameCube

Mayflash GameCube Controller Adapter for Wii U, PC USB and Switch, 4 Port

GameCube Controller Adapter Unboxing - Support Wii U, Nintendo Switch

Should I keep my GameCube on top of my Wii U or avoid that completely? : r/ wiiu

GameCube Broadband Adapter (BBA) support is now implemented in Nintendont. You can use either a USB LAN adapter or your Wi-Fi. : r/WiiHacks

Nintendont, Page 2028

Y Team Controller Adapter for Gamecube, Compatible with Nintendo Switch, Super Smash Bros Switch Gamecube Adapter for WII U/PC with 4 Port : Video Games

Nintendont, Page 2017