You may notice a new 
icon in the upper-right corner of the screen (on desktop only?). I installed a plugin to experiment with a forum chat. There are 3 chat plugins available, and they are geared toward a little different functionality. The one I installed first is to test a chat that is sorta like the Facebook chat on browser. It basically just piggybacks on the existing message system built in to the forums.
It is detailed here:
Another option, which provides group chat, is detailed here:
https://meta.discourse.org/t/babble-a-chat-plugin/31753
The third option, which provides a connection to various external chat services (Slack, Telegram, Discord, Riot, etc.) for the purpose of notifications is detailed here: