So here is the facebook documentation..
It seems to be saying you can output a Facebook WebGL build from Unity and upload it. It does not work for me, I get this message when I upload.
"Games must reference one of our supported SDKs via our CDN."
Theres also this thread, with people saying it is not supported.
https://forum.unity.com/threads/facebook-instant-games-support-html5.499198/
Yet the latest version of Unity has a WebGL option when building to Facebook platform.
What is going on? Does or doesn't this work?