So Nintendont was updated to support the GC adapter for Wii U

4 Port GameCube Controller Adapter for Nintendo Switch Wii U PC Super Smash Bros

GameCube Controller Adapter Unboxing - Support Wii U, Nintendo Switch

GameCube Adapter doesn't work with Nintendont. : r/WiiUHacks

Is it possible to connect Nintendo GameCube controllers to a Wii (not a Wii U) with some kind of adapter? If so, can you send a link? - Quora

USB Replica Nintendo Gamecube Controller On Nintendont

Connect two GC controllers to a Wii or Wii U system. Built in Turbo. Compatible with all games supported by the Wii Classic Controller, Wii Classic

Mayflash GC Controller Adapter for Wii & Wii U (Dual Pack), White

Controllers Compatible with Nintendont : r/WiiUHacks

GameCube Adapter doesn't work with Nintendont. : r/WiiUHacks

How to use a Wii as a GameCube - Quora

gamecube Controller Adapter (For Switch/WiiU/PC) – YCCTEAM