LG was very good at its attempt to get Android version 6.0 (also known as Android M or Marshmallow) to its customers early. In fact, if it wasn't for certain problems that it had upon its initial release of Marshmallow, LG would have been the first to receive the Android upgrade right after Google's own Nexus series. This is what is currently known about Android M Version 6.0 Marshmallow and Android N Release Dates for LG G5, G4, G3, G2, G Stylo, and V10 on T-Mobile, Sprint, Verizon, US Cellular, and AT&T.
With LG G5, the current flagship phone, arriving out of the packaging complete with Android M on board, it is only a matter of the trickle-down effect goes to all the LG phones that are going to get it. LG G4 users are pleased to have it as all five major carriers have rolled it out.
This also goes for the LG G3, which should have its Marshmallow upgrade taken care of as of last April, and it would appear that the popular V10 is taken care of as well. This would apply for carriers of these two LG devices, which include AT&T, T-Mobile, and Verizon.
What about the LG G Flex 2? There is word that it will be coming, but Tech Radar says there is "no official word", but the LG G4c has it. It would also appear that the LG G4 Stylo is getting the upgrade, as well as the LG G Pad X8.3.
The best advice one can give is if you have a newer LG Android device, it would be worth your while to check the "Settings" menu along with the "System Update" to see if the upgrade is available. It looks like things are progressing very well for LG, and it shouldn't take long before all of the newer devices have Android M on all carriers, assuming that it isn't already.
A recent report from Know Your Mobile mentioned the possibility of Android N coming to at least the LG G5. Considering that Android Marshmallow arrived for the LG G4, last December 2015, we can probably expect a repeat of that pattern. This would meant that Android N would arrive for the LG G5 sometime in December, hopefully as an early Christmas present. We will have to see if that is true, and it will probably take until later in 2017 before Android M comes to older Android devices.