This page describes the many different environment loaders and the different ways to mod your Wii U
Tiramisu is the most common way to mod one's Wii U.
Learn how to install Tiramisu at wiiu.hacks.guide. Tiramisu requires one to use the Homebrew Launcher to launch different Homebrew apps.
Haxchi and Coldboot Haxchi
Haxchi and Coldboot Haxchi is an older method of Wii U modding and requires one to own an Nintendo eShop DS game. eShop games cannot be purchased after the 27th of March 2023 thus making this way of modding impossible after that date.
Follow this guide to learn how to install Haxchi and Coldboot Haxchi on your Wii U. Haxchi and Coldboot Haxchi also requires the Homebrew Launcher to launch Homebrew apps.
Aroma is a fairly new modding tool used in a Wii U being only in beta at the time of writing this article. It is an Homebrew environment and thus requires the EnvironmentLoader from Tiramisu to be installed on the console.
The official Aroma website has instructions on how to install Aroma on one's Wii U. Aroma doesn't not require the Homebrew Launcher to lunch Homebrew apps as it installs a plugin that puts apps directly on the main Wii U menu.
The basic feature set of Aroma can be easily extended by the use of plugins. Plugins are run at all times when the Wii U is booted and greatly add support for the Wii U console. Plugins include things like launching games region free, pairing game pads region free, running a FTP server in the background and as mention before putting Homebrew apps directly on the Wii U menu.