this is a custom renderer. "react" does not know what a "div" is, this comes from "react-dom", that is why they have split these two packages apart.

but they also allow you to make your own renderer (https://github.com/facebook/react/tree/main/packages/react-r...) which then defines its own elements. you can try a mini threejs renderer here: https://codesandbox.io/s/reurope-reconciler-hd16y