Nintendon't is not a section of USB loader GX , is a standalone homebrew. Check out this thread to configure Nintendon't
https://gbatemp.net/threads/nintendont.349258/ , in the first page there's a very well made guide plus links to download latest version of Nintedon't.
Then you can configure USB loader GX or Wiiflow to load Gamecube games through Nintedon't.