Well I'll be damned, It works!
Nintendont does include a config file with the correct PID and VID of my adapter which is this one:
https://github.com/FIX94/Nintendont/blob/master/controllerconfigs/controller_Generic_GC Controller Adapter.ini
But it wasn't working...
I couldn't find a good HID Test program on PC, but with the one I used, for the most part, showed that all the buttons were correct.
-Nobody could explain what Polltype is except that only PS3 uses '0', so I left it to 1.
-DPAD from what I understand, if it's set to '1', you have to input 8 directional values instead of 4. I left that alone.
-DigitalLR you only use it '= 1' if your controller doesn't have analogue triggers. I have NO CLUE why that one has it and is set equals to '2' or what that means. I just deleted it. I don't know if that is what helped.
-Lastly, there is the MultiIn and MultiInValue. I didn't understand this one either. It's for adapters of multiple controllers such as this one. The most I could understand is that both set to '1' (I don't know why one of them is set to '01') should work when you're using one controller, and that if you want to use more controllers you should change the MultiInValue, so I changed that one to 4.
The weird thing is that the official adapter's config has those set as '3' and '09' as you can see here:
https://github.com/FIX94/Nintendont...ontroller_Nintendo_Wii_U_GameCube_Adapter.ini
I have no clue why that it or what it does, except that I tried it set to those values and the Nintendont menu gets stuck as if you're pressing upwards.
Apparently with the official adapter you can control the Nintendont menu, You would know since you said you had it.
I don't know what did it or why, but it works. Going to check with a real Gamecube if the sensitivity feels the same and I'm researching if I can enable rumble using these: Rumble= RumbleType= RumbleDataLen= RumbleDataOn= RumbleDataOff= RumbleTransferLen= RumbleTransfers=
Does your rumble work using Nintendont and the official adapter as is?