Preparations and some important notes:
This guide is can only applied for T-Mobile LG G4 with H811 model number smartphones. Please, do not attempt to flash it with any other LG or Android device.
Make sure you’ve rooted your T-Mobile LG G4 and there is any custom recovery image. You can choose TWRP, CWM or other recoveries installed. Because without those two requirements you won’t be able to flash this ROM.
In the end, it it preferable to plug in charger your LG G4 if it shows less than 20% battery backup.
Did you noted requirement above? If yes, go ahead follow these steps carefully.
1. Download Lineage 14.1 for T-Mobile LG G4 (Nougat 7.1.1)
As mentioned above Android 7.1.1 Nougat is a major update so, it is required big ROM file, so you need to connect your LG G4 to a free Wi-Fi network to be able to download the ROM without worrying your bill data costs increasing.
Download LineageOS 14.1 for T-Mobile LG G4 (H811)
Choose the latest build for the better.
2. Download GApps Nougat for Lineage 14.1
Most custom ROMs are not including Googles Apps. It's aplied to Lineage OS as well. You'll need to flash GApps package to your T-Mobile LG G4 yourself to be able to enjoy any Google service as well.
Download Lineage OS 14.1 Nougat Gapps
We recommend you to choose Pico package as it the smallest one.
3. Installing Lineage OS 14.1 T-Mobil LG G4
After you've downloaded both the Lineage OS 14.1 ROM and Lineage Gapps from before, transfer them to your phone’s internal storage.
Power off your LG G4 completely. Don't enable quick boot feature.
Then, boot it into recovery mode using hardware buttons.
Now you are in the TWRP Recovery main menu, you need to hard reseting the phone. From the TWRP main menu tap on the wipe button and select Advanced Wipe. Then select all Dalvik cache, System, Data and Cache options.
After this task complete; go back to TWRP main menu and tap on the install option then navigate to the Lineage OS location you’ve downloaded previous and flash it by swipe to the right button at the bottom.
Wait for minutes until its done, then go back again to TWRP main menu tap on the install option again but this time coose Lineage OS Nougat Gapps file and flash it.
In the end, just reboot your phone after flashing proccess done.
And now you can enjoy Lineage OS Nougat 7.1.1 on T-Mobile LG G4 with GApps service works.