I've just bought one solely to enable better access to music and photos on my Xbox One than DLNA native from my NAS can provide... only to find that the XBox One app supports neither music or photos!! No mention of this in the features pages at all!!
Send an email to "plexpass @ plex.tv" with your request.
For what is and isn't supported on the pre-view version of the Xbox app see;
https://support.plex.tv/hc/en-us/sections/200642446-FAQ-Plex-for-Xbox-One
While communication over what features apps do or don't have is quite frankly terrible at the moment both the company and the community are working through some ideas on how to better communication going forward.
Also the xbox apps are going to be getting those features at some point, but nobody knows when yet.
We're currently working on this:
https://forums.plex.tv/topic/153113-client-capabilities-chart/
Any input is greatly appreciated!
EDIT: It's not very pretty yet, but we're still in the info gathering phase.