Many users are still waiting to hear news about when their devices might be updated to the most recent version of the Android operating system called Android 6.0 Marshmallow. LG was one of the first companies to release such update for a few of their devices. The LG G4 from Poland started getting updated just a couple of weeks after Google released the software to be modified by OEMs. This handset has been receiving the update in additional regions ever since, including Canada and some European countries. In the U.S., the Sprint variant of the LG G4 started receiving updates in December and now, it seems that the software can be installed in various T-Mobile units.
T-Mobile's Software Update support page still states that this particular update is in the Manufacturer Development stage for the LG G4. In this stage, manufacturers modify some aspects of Android including customizing some features and the way it looks besides making sure everything works as it is supposed to. Then, they submit the final build for carrier approval and then it gets released for the locked devices of that particular carrier. The strange thing is that despite the current status reported by T-Mobile and the lack of an official announcement from LG, some users from Reddit and xda-developers have been able to get Marshmallow on their LG G4s by installing it from the LG Bridge software.
LG Bridge is used to manage content between the phone and a PC as well as updating mobile devices, so apparently, users just need to plug their phone into their computer and they will be prompted to download the update, although it may not work for everyone just yet. If you are curious, you can download LG Bridge from the link at the source and try for yourself, the update should appear as H81120I. The over-the-air update is not rolling out at the time, so LG may have sent the update to some users in order to test it. Still, the update for T-Mobile variants of the LG G4 might be ready quite a bit sooner than users think.