My Wii U is on version 5.5.3 and is homebrewed without Haxchi
I have SDcaffine on my SD card. Mario Kart 8 Mods & Super Mario Maker Mods work for me
Smash is the only game that refuses to work with mods. I basically add the mods the same way as MK8 and SMM and when I load into Smash 4 it shows which mod i'd like to load. But nothing is different after that
Unlike modding MK8 and Mario Maker, Sm4sh Wii U requires a long process to start even loading mods onto there. Fortunately, there are some tutorials on here that can help with getting started with modding Sm4sh Wii U. This is the latest tutorial I can find on that matter, but you can search different tutorials to see what fits you.