The only viable emulator for Wii U games today is (available for Windows, Linux, and macOS via Wine/Crossover).
has officially closed, making it impossible to purchase digital copies of the game. The game was actually delisted from the digital storefront even earlier, around late 2019 or mid-2020, likely due to licensing agreements for the Nintendo-themed content. tekken tag tournament 2 wii u iso
However, I can offer a for playing the game legally, and explain the technical context for those who own the original disc. The only viable emulator for Wii U games