Ok hear me out. But I had been installing the different sig patches listed in the thread and nothing worked. Every time I tried booting into Animal Crossing it continued to give me the 'Unable to Start Software" "Return to the Home Screen" bs message. So I literally did a shit ton of digging for a few days and stumbled upon something that ended up working for me. Not sure if it will for any of you guys but it's worth a try...
So what I ended up doing was holding down the power button with the switch still on and pressing power options. Now you're going to want to press restart and you want to boot into Maintenance Mode (hold the both + and - volume buttons down at the same time) while it's going through the bootloader screens and past the Nintendo Logo screen. It should pop up with a menu that has three different options, reset all settings, delete all saved data, etc... IGNORE all of those options. All you need to do is press the power button again and then upload your payload and wait for the switch to boot again. Once you boot try and start the games again, Animal Crossing or Pokemon... Animal Crossing absolutely refused to run before I tried this method and I installed it multiple times with every single update as well along with different sig patched because I was unsure about primary vs secondary. This fixed it for me...