CyanogenMod team has released the official CM 14.1 Nightlies for all the AT&T Galaxy S3 smartphones.
In case you're looking for a custom ROM that can install the latest Nougat firmware for your old Galaxy phone, then this is the one you should flash.
The CyanogenMod 14.1 Nightlies are based on the latest Android 7.1.1 Nougat releases, but you need to know that there are in no way final builds. Note that you will find errors and bugs while running the CM 14.1 Nougat Nightly builds, and you should report them back to CyanogenMod developers all the errors you find while testing the new files.
Read the following guidelines before starting the installation of CM 14.1 Nightly:
- use this tutorial only with the Samsung Galaxy S3 AT&T models.
- do not try to update any other different devices with the files that you will find in this post.
- your phone has to run a rooted firmware, and it should run a custom Recovery image like TWRP Recovery.
- the installed custom Recovery has to be upgraded to its latest version, so that it supports the newest Nougat 7.1.1 custom ROM installations.
- in the tutorial you will find two extra steps: the NANDROID Backup for the installed ROM and the Factory Reset ones.
- the NANDROID Backup creates a full restore point for your device, one that you can use in case the new custom ROM doesn't boot in normal mode after the installation is done.
- the Factory Reset process wipes clean the system partition, it removes the old ROM and it forces CM 14.1 Nougat Nightly to boot in normal mode.
- Factory Resetting the smartphone won't delete any data from internal storage of your device.
- if you need to save data from installed applications you can use the Helium tool for Android devices.
- check your phone's battery charge levels and make sure that there is at least 50% charge left before the smartphone powers off successfully.
- this tutorial should be used only by advanced users, we cannot be blamed in case you brick the phone nor in case you lose any data in the process.
Since you've read all of the above you can continue to the next part of this post.
How to flash Cm 14.1 Nightly Nougat Custom ROM for AT&T Samsung Galaxy S3:
- Download CM 14.1 Nightly zip file from here.
- Download Gapps for Android 7.1-based ROMs from here.
- Move both files to your phone's internal storage. Do not unzip the files.
- disconnect the phone from PC.
- Switch off your device.
- Boot the AT&T Galaxy S3 in custom Recovery Mode.
- Create a NANDROID Backup for the ROM that is installed on your device. From TWRP select 'backup and restore' option.
- Now you can Factory Reset the device: select 'Wipe' options menu. Confirm process.
- Start CM 14.1 Nightly Nougat installation process: find and load the CM 14.1 Nightly zip file and load it in Odin.
Confirm the flashing process.
- After the custom ROM is done installing you can flash the Gapps zip file, too.
- Reboot your smartphone in normal mode after all the files are done installing.
- note that the first boot process will take a while before it loads all files.
- Use your usual Google login data in order to unlock the device.
After the installation of CM 14.1 Nightly ROM is done you can continue flashing future new CyanogenMod releases using the CM Updates section of your device.
If you need any extra help completing the tutorial then you should tell us in comments below.