Matchmaking may not be fixed yet but that doesn’t mean you can’t play Halo.
Stop by halocustomgames.com, enter your information and start sending out invites. I’ve written a brief tutorial on how to use the site and how to send messages in Xbox live. So that if you are new to the Xbox One or you just need some help finding the right buttons to push here’s a link:
http://little-ogre.kinja.com/halo-custom-games-a-how-to-1660900361
*I apologize for the inconvenience but links appear not to be working at the moment for me.