The OnePlus 3 is a great flagship that costs around $400, but, currently, it runs on Android 6.0.1 Marshmallow, and it’s not sure when it will receive the 7.0 Nougat update. Until then, owners of this device can install the unofficial CM14 ROM and play around with Nougat’s new features. Since this isn’t the final version of the custom ROM, it will come with bugs and will offer an unstable experience.
The Android 7.0 Nougat-based CM14 build was posted on Xda and it was created by HatRiGt, Senior Member in Xda. Currently, the custom ROM is in alpha stage and it’s not really stable, but relatively functional, so if you want to install it, follow the instruction below:
Before installing CyanogenMod 14 (Unofficial) on your OnePlus 3, make sure that the device’s bootloader is unlocked, and get a custom recovery (TWRP/CWM). Now, download the custom ROM from here and GApps zip file from here. Next, you will have to connect your OnePlus 3 to your PC using a USB cable and copy and paste the downloaded file to the internal memory of the phone.
Restart your OnePlus 3 and boot into Recovery mode, and from the TWRP menu select “Wipe”, then select “Swipe to Factory Reset” from the bottom of the screen. After that, return to the TWRP main menu and tap on “Install” button, then go to the location where you’ve saved the CM14 zip file, select it and do “Swipe to Confirm Flash” from the bottom of the screen. Now, the custom ROM installation process will begin and it will take a few minutes to complete.
After the ROM is successfully installed, you will select the “Wipe cache/dalvik” option, then “Swipe to wipe” and you will follow the same steps to install the Nougat Gapps file. In the end, from the TWRP main menu you will reboot your device and it will run on the Android 7.0 Nougat-based CM14 build.