From the day I've bought the G6, the option for enhanced messaging has been absent of this phone. I had it on my old HTC phone.
Enhanced messaging is disabled for now on the LG G6 though Android Messages does have some of that functionality. It is expected to be enabled sometime in the near future but I don't have a specific date.
In light of Sprint's press release of Nov. 4, 2016 (http://newsroom.sprint.com/sprint-is-the-first-carrier-to-launch-rcs-messaging-with-google.htm), I think an explanation is owed.
"Next year, all new Android devices from Sprint will come with Messenger for Android preloaded as the default SMS and RCS messaging experience."
In my reading, that's a broken promise.
Is there any word yet as to when they will add this to the G6? My fiance has the S8 and she's got the enhanced features however I still do not on my LG G6.