How to do gouraud shading?

But wouldn’t unlit disable all lighting and shadows? I need gouraud shading for a project aiming to recreate an older style game. I have been told you can do it in a material node graph but can’t find any solid information on how to do it. Every tutorial about this is only for “PS1” style flat shading, that doesn’t work well for my purpose as each polygon is clearly visible as if no smooth shading was used at all. The visual style I am targeting is that of 6th-gen consoles like the PS2 and Gamecube. Those consoles only really used gouraud shading and not a more advanced phong shader like we have now. But they also aren’t “flat” looking like a PS1 or N64.

I quoted a post from back in 2015 that gave a vague explanation, but no real implementation of the node graph. I am looking for a good explanation of the nodes I will need to do what was said in that post.