Sprint has posted the update details for Android 5.1.1 on the LG G Flex 2, which will be great for the handful of people who have one. It seems like this update started rolling out about a week ago in a limited fashion, and no one noticed, but now it's available widely.
According to Sprint, the 5.1.1 update for the G Flex 2 includes factory reset protection and the standard 5.1.1 Lollipop features. Very informative, Sprint. Presumably that means things like improved heads-up notifications and interruption settings.
The update comes with build number LS996ZV6 and should be available in your system update menu. That is, of course, assuming you have a G Flex 2, which you probably don't.