what the heck

Can you give the reference of the mod? Is it playable on physical Wii U?

Yes, this is running on my Wii U. Research "sdcafiine" and how to use it to load mods on-console. Many say that sdcafiine won't work on Aroma, but I've found this not to be true if using the sdc plug-in from the Homebrew Store.

When browsing for mods to use on Wii U, look for older uploads that use the game's native file format/names for the assets to be modded. Most modern BotW mods are dev'd for Cemu/Switch and will not work on Wii U. This Linkle mod is very old, so it works on Wii U.

Many thanks for the answer. As you said, quite old or simple mods will run. I've tried relics once but it was way too slow to load.