T-Mobile has started seeding Android 6.0.1 Marshmallow based January Security update for it’s LG G4. The update carries build number H81120r, weighs about 90MB and is rolling out via OTA. These monthly security updates are important as it ensures security of the device from Viruses and Malware. If you haven’t received the OTA notification then unlock your device and go to Settings > About phone > Software updates.
Tap on check for new firmware updates, if the H81120r firmware is available for your device you would be notified, just download and install it on your device. The T-Mobile LG G4 is not receiving the expected Nougat firmware but if you are good at flashing custom ROMs then we recommend you to try the latest Lineage OS 14.1 ROM on your device. By installing the Nougat custom ROM your device you can get a glimpse of latest Android 7.1.1 Nougat firmware on your device.