LineageOS 14.1 brings Android 7.1 Nougat operating system to the LG G3 phone. This is designed to give you great performance and reliability over the stock android for your device. It is based on AOSP project which means you will getting vanilla android experience on your LG G3. And since the LineageOS is barebones, you have the option to use it without google services as well. Of course, you can flash gapps immediately after installing ROM so that you get all google services onboard.
Download latest version from here http://download.lineageos.org/d855
Gapps link http://opengapps.org/ (Platform: ARM, Android: 7.1, Variant: nano)
Make sure your computer has working adb. Setup instructions can be found here.
Enable USB debugging on your device.
Now, make sure you have rooted your G3 as that is important for next step. You can follow this guide if you have not. After, you need to have LG G3 TWRP recovery onboard as this is required to flash custom ROMs.
Download the LineageOS install package that you’d like to install or build the package yourself. Download gapps as well if you want to run Google services.
Place the LineageOS .zip package, as well as any other .zip packages on the root of /sdcard
With the device powered off, hold Volume Down + Power. Release all buttons and press Power again as soon as the LG logo appears. This will take you to recovery.
Navigate to /sdcard, and select the LineageOS .zip package.
Follow the on-screen prompts to install the package. Optional – install gapps package.
Reboot after package installation is finished.