Place the following line in your ~/.bashrc file:

export SDL_GAMECONTROLLERCONFIG="0300000057696920552047616d654300,Wii U GameCube Adapter Port 1,platform:Linux,x:b3,a:b0,b:b1,y:b2,start:b7,dpleft:b10,dpdown:b9,dpright:b11,dpup:b8,lefttrigger:a2,rightshoulder:b6,righttrigger:a5,leftx:a0,lefty:a1,rightx:a3,righty:a4,"

This will provide an automatic controller configuration for games that use the
SDL_GameController API within SDL2. While the controller name implies that this
is for the first port only, this configuration should work with any number of
devices.

Note that the following inputs are not supported, due to the controller's own
limitations:

SDL_CONTROLLER_BUTTON_BACK
SDL_CONTROLLER_BUTTON_GUIDE
SDL_CONTROLLER_BUTTON_LEFTSTICK
SDL_CONTROLLER_BUTTON_RIGHTSTICK
SDL_CONTROLLER_BUTTON_LEFTSHOULDER

For more information about the SDL_GameController API, visit the SDL wiki:

https://wiki.libsdl.org/CategoryGameController