READ ME: I am not responsible for bricked/damaged devices from following this procedure. It should be safe, if done right on the supported models. This does not void your warranty, but it is soak test firmware, meaning that it is beta software, and might have bugs/issues. I haven't noticed any myself, however.
Alright, I am aware that there are already videos describing how to install Nougat, but this is a (fairly) easy to follow text tutorial.
Step 1: Make sure your running the latest Marshmallow.
Before you can install the Nougat update, you have to make sure that you are running the latest Marshmallow firmware for your device. If your phone is running the MPJ24.139-63 firmware, you are good to go. Anything lower, and you will have to update your firmware, either manually, or through the OTA checker.
UPDATE: Download this file and flash it in recovery the same way that you install Nougat, to update to the latest Marshmallow firmware, if you are on anything lower than MPJ24.139-63: https://docs.google.com/uc?export=do...ER0cml3VzRHZTA
Step 2: Download the Nougat OTA File.
Follow this link to download the Nougat OTA file: http://downloadmirror.co/Uq5/Blur_Ve...tail.en.US.zip
Step 3: Boot into Recovery.
You have to boot into recovery to sideload this OTA file. First, power off the device completely. When it is completely powered down, hold the Volume Down button, and then the power button, not letting go of either button, until an Android appears, with a bunch of text. You are now in Fastboot Mode. Press the Volume Down button until you see Recovery Mode, then hit the power button.
Step 4: Install.
Once you are in Recovery, you may see an Android logo again, with the text "No Command" below it. What you need to do here is hold the power button, and whilst holding the power button, press Volume Up, to access the menu. It is easy from here. You need to select the option to install update from SD Card, using the Volume buttons for navigation, and Power to select. From there, you find where you downloaded the BLUR_VERSION.24.31.64.ATHENE.RETAIL.EN.US.ZIP file, and select it. It will start installing the official Nougat OTA. Give it some time, upwards of 15 minutes to install. Once it has complete, simply select the Reboot system now option, and if all went well, you should see the "Android is upgrading" screen, and now you are running official Nougat soak test on your G4.
NOTES - The install may hang on the "Patching system image after verification." message. Give it around 5-10 minutes, it will eventually pass that stage.
I can't guarantee that this method will work on all G4 variants. I can confirm it works on a UK Retail XT1622, however.
This may make it harder to install the stable official Nougat when that releases worldwide, I am not sure yet if it affects the upgrade path to the stable firmware.
I actually have not found any issues with this firmware yet, it appears VERY stable for a soak test build. If you have come across any, or need help, comment below.
These models have said to have had success with this update.
XT1643 - Moto G4 Plus Dual-SIM (India)
XT1640 - Moto G4 Plus Dual-SIM (Brazil)
XT1642 - Moto G4 Plus
XT1622 - Moto G4
XT1626 - Moto G4 (India)