d2x only shows v3, v4, v5, and v6. Below I have attached the d2x Installer that I am using. I have also tried the one from wiiu.hacks.guide and a few other ones.
SD: 64gb FAT32, Write feature works
Edit: I have also tried it with a 4GB SD card.
I found that on 3DNUS if you type in "12.0.0-40U" for the USA region it will start to download some files. I really do not know if it is really 12.0 though.