It allows the injection of a payload that lets one run unsigned code on the Wii U, achieved via a Raspberry Pi Pico. The Pico is ultimately used to boot off an SD card running a recovery program ...

Facepalm: When Nintendo released the Wii ... Wii U is through the ISFShax exploit, which can redirect the console's system memory to a properly formatted and pre-configured external SD card ...

We loved [banjokazooie]’s RetroPie Wii U mod, and happy to see them back again ... Bluetooth, WiFi, a 128GB SD card slot, two 3.7V 4000 mAh batteries, a Pololu 5V,6A step-down voltage regulator ...