Yesterday, LG has officially added its latest flagship G6 to the list of smartphones that supports bootloader unlocking officially. Anyhow, this is specific for the G6 European variant, which carries the H870 model number.
For the uninitiated, bootloader unlocking lets you do things like running a custom ROM on your handset. Unlocking bootloader of LG G6 will void your phone warranty, and you won't claim it back.
Below or the steps to unlock the bootloader. Don't try this is any other device as it might get bricked.
Things to do
Make sure your device has at least 50% to 60% charge. To enable Developer Options, go to About phone and tap the Build Number 7 times. Next up is enable 'USB debugging' and 'OEM Unlock' option from Setting -> Developer option. Now install the ADB and fast boot driver for windows or ADB and Fastboot for Mac.
Step 1: First of all, you need to create LG developer account
Step 2: To unlock the bootloader, you need two things -- device ID and IMEI number.
Step 3: Go to installation directory open ADB folder and open the command window by pressing 'shift' key and right-click.
Step 4: Connect the phone to PC and reboot the device into bootloader mode by typing "adb reboot bootloader"
Step 5: Once it goes into the bootloader type "fastboot oem device-id"
Step 6: The above command will give you a string character which is the device ID.
$ fastboot oem device-id
Step 7: Now copy paste the device ID in one line without any writing bootloader or space.
Step 8: Once done head on to LG Developer website and log into your account and click the Start Unlocking the Bootloader button.
Step 9: Now enter all the details including name, email ID, IMEI and device ID.
Step 10: Select your device 'LG H870' and click on 'Confirm'.
Step 11: Now you get the Unlock key on your mail. Download it and save it on your fastboot directory.
Step 12: If your device is in fastboot mode and connected to the PC enter "fastboot flash unlock unlock.bin"
Step 13: Now reboot your device by typing " fastboot reboot"