Does it count as an emulator? Or does it count as a different platform?

I imagine the mods could just add Switch as a platform, but in case they don't, you could add it under NESClassic, since that's using the same emulator and I don't think Ninja Gaiden is one of those games that was changed for Online features.

^ agreed. I'd assume it would be added as either a separate platform/ category or merged with the NES Classic.

Added Switch