But since you are not on a carrier why update?
And let me share that I'm on Ting.com so I can control the data on/off at Ting.com as well as my phone. Updates just work and I have the data portion turned off and it gets it over WiFi.
About those that say yours has 5.11. This is a royal mess as one AT&T LG G Flex 2 may not be the same as a run of the mill factory unlocked paid full price LG G Flex 2. I'll also not write about XDA Forums where you can get other roms.
After the Fire Phone no Prime fiasco I returned it and bought an unlocked AT&T LG G Flex 2. I've never owned a smartphone before and have made due with my old dumb phone and iPod Touch. I see that many of these phones need to be updated through the carrier. I ran the LG software and it says the phone doesn't need an update. Everything I've read says the phone has been updated to 5.1.1 and is supposed to receive a 6.0 upgrade down the road. Will putting in an AT&T sim allow it to update? If not do I get a month's of AT&T service to update the phone and then go for something cheaper? I really don't use wireless much, I rarely go above 60 minutes a month. I'm more concerned about data when there's no Wi-Fi around. AT&T and the virtual providers that use their network is the only GSM service around here. If I went with Cricket would it update through the AT&T network? What do I have to do to update my phone?