Step 2: Place the Android Nougat ROM into the phone’s storage memory.
Step 4: Perform Recovery mode sorties by long pressing Volume (Down) + Power key Simultaneously
Step 5: Once entering the TWRP settings menu, clear phone’s memory (full) by selecting ‘Wipe’ option. Once done, select – ‘Swipe to Factory Reset’ perform factory reset
Step 6: Return to TWRP settings and tap ‘Install‘ and Selecting Downloaded Lineage.Zip file.
Step 7: Approve the installation by tapping ‘Swipe to Confirm Flash’
Step 8: Flashing of the ROM begins and after few minutes, a message ‘Successful‘ appears on the screen, thus completing installation.
Step 9: Return to TWRP settings and tap ‘Install’ Select Downloaded GApps.Zip file in the phone’s memory.
Step 10: Approve the installation by tapping ‘Swipe to Confirm Flash’
Step 11: Reboot your Mobile
Note:- If faced with boot loop problem, navigate back to TWRP settings, and select ‘Wipe cache/dalvik’. This procedure will help resolve any issue with regard to custom ROM installation.
That’s it! Your LG G3 T-Mobile (d851) should now have Unofficial Lineage OS 14.1 ROM installed on your phone! Go to Settings > About phone to verify.