Mayflash is usually the way to go.
Gamecube controllers take a bit of setup, but there are guides everywhere on how to do so.
I personally prefer the Pro Controller. Just flip a switch on the side of the adapter and you're using Xinput. Pretty much no setup.
thanks, updated links, just the wii u one: https://smile.amazon.com/Mayflash-Wireless-Wii-Controller-Adapter/dp/B00E6553PW/ref=sr_1_2?dchild=1&keywords=wii+u+pro+controller+adapter&qid=1614752094&sr=8-2
i dont want to use wiinusoft, as i had trouble using it and ds4windows together at the same time
thanks, it looks like the pro is more future proof
I love the Wii U Pro controller for retro gaming. I much prefer its d-pad to the Switch Pro's. As such I use this adapter to connect:
https://www.amazon.com/Mayflash-Wireless-Wii-Controller-Adapter/dp/B00E6553PW
I got one of these to use with Wii U controllers and it works well.