CyanogenMod 12.1 ROM
CyanogenMod 12.1 ROM for LG G3 D855.XDA

The unofficial CyanogenMod 12.1 custom build is ready to download for the international European model of LG G3 (D855), which is running Android Lollipop version 5.0. Like any other beta version, this ROM also has bug issues and cannot be used as a daily driver.

Senior XDA member LastStandingDroid who shared it (build released by LifeWalker) has confirmed that data connection and Wi-Fi are not working in this build.

If you still want to experience the beta Android 5.1 firmware ahead of the official release, check out the following installation guide.

Points to remember

  • Before following the installation guide, create a backup of all important data of the phone using custom recovery.
  • Enable USB Debugging on the phone to connect it with the computer and use Android SDK with it. [Navigate to Settings>> About phone. Tap on Build Number several times until a message appears saying 'You are now a Developer.' Now enable USB Debugging Mode by navigating to Settings>> Developer Options.]
  • Your LG G4 should have above 80% battery charge to avoid power off during the process which could damage the device.
  • The phone should be rooted with the latest recovery system installed on it. Also, it should have an unlocked bootloader. [The guide below uses TWRP recovery.]
  • The CyanogenMod 12.1 ROM is in its alpha stage, therefore, all the features might not function properly.
  • The Android 5.1 CyanogenMod 12.1 beta firmware works with LG G3 European model D855 only. Flashing this on any incorrect variant might brick the device. Therefore, verify the model number of the device.
  • After flashing the ROM if the device gets stuck on booting animation or if you experience boot loop then perform wipe cache partition and wipe dalvik cache for a few times before rebooting the device.
  • Once the ROM is installed, users are advised to give 10 minutes to the ROM after the device boots up for the first time for better user experience.

Download files

CyanogenMod 12.1 ROM [Alternate link]

Gapps

How to install unofficial CyanogenMod 12.1 with Android 5.1 Lollipop on LG G3 D855

Step-1: Connect the LG G3 to the PC using USB cable and then transfer the downloaded files to the phone's storage. Keep the files in the SD card root, not inside any folder

Step-2: Unplug the USB cable from the phone and switch it off

Step-3: Boot the phone into recovery mode. Press and hold Volume Down and Power buttons together for a few seconds. When the LG logo appears, release the buttons then press them again. Then press Power button three times to boot into recovery mode

Step-4: In TWRP recovery, create a Nandroid backup. Select backup then do a swipe on the Swipe to Back Up option at the bottom of the screen

Step-5: Perform a full wipe, which includes Dalvik Cache, Cache, System and Factory Data Reset

Step-6: Once the process is completed, return to main recovery menu and select Install. Head over to the folder where you have saved the unofficial CM12.1 ROM, select it and swipe the Swipe to Confirm Flash option

Step-7: When the installation is completed go back to the main menu and select Reboot>> System

Step-8: Download Gapps, if you have not done so already

Step-9: Follow the same procedure as mentioned in Step-6 and flash the Gapps package

Step-10: Finally Reboot the phone

You would now be able to enjoy Android 5.1 Lollipop features through the beta CM12.1 ROM on your LG G3.

[Source: Android Soul]