The latest firmware for LG G4 H811 is Software version H81120x,Android 6.0.1.
The Update H81120X was released on December 5, 2017.
Starting February 4, the T-mobile LG G4 received an update to software Android 6.0 / Software H81120i available via OTA push and pull-down.
You can download and install the software update From the phone.
If you want to update your LG G4 to Android 6.0 by flashing the stock firmware, From below link you can download the stock LG G4 Android 6.0 firmware H81120i.kdz
Download /H81120i.kdz from LG Server: H81120i_00_0201.kdz
To learn more about the T-mobile LG G4 H811 Software Update instructions, please visit: https://support.t-mobile.com/docs/DOC-22421
The Update is also available for download from “LG Bridge”.
Will my LG G4 H811 receive Android N 7.0 software Update?
The LG G4 H811would not be updated to Nougat.
“We decided not to Provide Android 7.0 (7.0 & 7.1) update for G4 and V10. As a result of internal compatibility with the new Android system, it was concluded that it is difficult to maintain optimized performance.”
— said an LG Official (source)