It looks like LG is ahead of the game when it comes to getting its devices the latest version of Android with version 6.0 (also known as Android M or Marshmallow). However, there is a lot of information abounding as far as what countries and what carriers have it, or going to have it. Here is the latest news about the Android M Version 6.0 Marshmallow Release Date for the LG G4, G3, and G Stylo on Verizon, AT&T, T-Mobile, US Cellular, and Sprint.
According to the Lawyer Herald, LG is continuing its Android 6.0 Marshmallow upgrade to the G4 series, at least in Canada. It also reports that G4 units in the United States have been "left hanging with the official over the air (OTA) roll out of Android 6.0 Marshmallow when it was cut from Sprint and US Cellular".
Hopefully, that isn't a permanent cut, but it is believed that the G4 should be receiving its Android M upgrade on AT&T, T-Mobile, and Verizon before February 2016. It is also believed that AT&T should get the update first, followed by Verizon and T-Mobile, but not necessarily in that order on the last two. This is generally the case for an Android rollout as certain carriers have been known to get their devices an Android upgrade before others.
As it is, the G4 was promised to be one of the first to receive the Android upgrade by the company a few months ago, and Tech Radar reports that it is on board on European devices like users in Poland, Germany, Portugal, Spain, Romania, Austria, Switzerland, Hungary, Croatia, and Turkey. This source also reports that the Marshmallow upgrade is already out on Sprint in the United States, so perhaps there is some misinformation on the word "cut" on the report from the previously mentioned Lawyer Herald. The fact that Marshmallow has come to at least Sprint's LG G4 has been confirmed on Gotta Be Mobile, and they even reported on certain problems that happened to the device with the addition of the upgrade.
In addition to the LG G4, last year's current flagship device from the Korean company, there is a report that the LG G3, the flagship from two years ago, will be receiving Android 6.0 as well. There is also a report the LG G Stylo, a Galaxy note contender, has received its Marshmallow update rather recently.
Speaking of upgrades, LG G4 will soon find that their phone is out of date as Mobile World Congress 2016, a big annual event for mobile devices in Barcelona, Spain, is happening in early soon. Android Authority states that LG confirmed the launch date set for February 21st. No doubt the LG G5 will have Marshmallow out of the box, so hopefully the other LG devices will be caught up by then.