Devolution is a GameCube backup loader developed by tueidj. It was the first GameCube loader to work in Wii Mode and on Wii U. The loader has very high compatibility with games and supports full Memory card emulation.
Support thread: https://gbatemp.net/threads/devolution-public-release.330554/
Compatibility list: http://wiki.gbatemp.net/wiki/Devolution_Compatibility_List
A GameCube Compatible Wii (not the "Family edition" that lacks GameCube ports).
While Devolution works on the Family edition and the WiiU, you still need an old Wii to verify and rip the games.
A USB device or SD card for storing the games.
1. Download the Devolution package and extract it to the SD card. Merge the apps folder with the existing apps folder on the card if needed.
2. Devolution can be run from the Homebrew Channel directly, or it can be loaded from a USB loader. The USB loader may need to be configured to use Devolution as GameCube loader.
Devolution requires 1:1 disc images in order to work. This is so it can verify the games to assure it is legit.
Discs can be ripped on the Wii (must be a GameCube compatible Wii) using Cleanrip.
Games should be placed on the USB device (or SD card) in a subfolder of the games folder. For example:
If the game has 2 discs, place the ISO of the second disc in the same folder and name it gam1.iso
The first time launching a game, it needs to be verified to assure the image is valid. In this case, the disc slot should flash two times. You should then insert the original disc of the game (don't insert it beforehand). If successful, the disc slot should flash 5 times and the game will be verified. The next time you load the game, this procedure will not be needed.