Definitive Photon library reference

I acquired a Photon recently and I am struggling to establish exactly where the definitive library reference documentation is.

I know that the Photon is described as “Arduino compatible” but I am also conscious that not all Arduino libraries have been ported to the Photon. In the web IDE only 4 official libraries are listed and I’m sure there are far more than that.

How can I find out exactly what is available for the Photon and what is not?

You can try all the libraries that are listed in Particle Build - most of the community libraries are just doing what they are supposed to do.