Yes, Both freesync2 and gysnc2 support HDR. And that is fantastic. Needs to happen, and i'd like to know more about gsync 2 and freesync 2 for specs (nits,bits per channel, back light, etc)
But i'm still of the mind that they are both exclusive tech but with AMD just saying ((open monitor support (because it is free) Amd tech required) while Nvidia is both monitor tech and Nvida hardware. Amd is saying only hardware is needed so somehow we are 100% open. There is specific tech needed from AMD. AMD's own website says that.
AMD says they use standards in all there slides. But it is not a standard you need a certain tech (AMD) Just just needing to buy hardware in your monitor.