Owners of the LG G4 on T-mobile were starting to get annoyed at the lack of Marshmallow for their phones. Well, no longer. Some users have reported receiving the update via LG's update tool. And T-Mobile has added OTA information to its website.
According to T-Mobile, the OTA started yesterday (February 4th). It probably only hit a small number of devices and will continue spreading over the next week or two. If you don't want to wait, many users (myself included) have managed to get the Android 6.0 update via the LG Bridge application. You'll need a computer and USB cable for that to work, though.
The new software version number is H81120i, and you should get the OTA eventually if you're on H81120n, H81120h, or H81120d. When it's all over, the G4 will be on Android 6.0 with the January security patches.
Thanks: Jorge and Benny