Super Mario 3D All Stars has leaked onto the Internet.
— OatmealDome (@OatmealDome) September 15, 2020
It appears all the games are emulated.
Galaxy and Sunshine run under a Wii and GameCube emulator named "hagi"(?) possibly made by NERD (Nintendo of Europe division).
Mario 64 is running under an N64 emulator. Dunno which.