WUX Winner for Real Hardware (2021): WUP Installer
Note: This post reflects the state of the Wii U hacking and ROM scene in 2021. Since then, tools and servers have changed significantly. Always follow current guides and copyright laws in your region.
A “ROM” (Read-Only Memory) is a digital copy of a game. For Wii U, WUP-format installable backups function as ROMs.