The LTE variant of the Moto G 2014 and the 3G variant of the Moto E can be updated to CyanogenMod CM13, which is a custom ROMs based on AOSP of Android 6.0 Marshmallow. It was reported that the ROM has a few bugs that affect the features of each Moto device, preventing the users from using them.
The features that should work on the Moto E 2015 (3G) are the Display, WiFi, SD Card, GPS and audio (partial), while the broken features are related to the Camera, video playback, FM radio, RIL etc.
The features that work almost perfectly on the Moto G 2014 (LTE) are related to the Microphone, Audio, Video Playback, Bluetooth, WiFi, LED and RIL. The features that aren’t currently working: Stock file manager, Stock browser which doesn’t download files, Camera, Flashlight and when you’re trying to change the English language, this will cause a bootloop.
First, you will need to search on the internet for the following files: Android 6.0 Marshmallow CM13 ROM for Moto G 2014 (LTE) or for the Moto E 2015 (3G), and you’ll also use Google Apps or Marshmallow Gapps.
If you have other phone than the one we’ve specified above, this method won’t work. So, before installing the Android 6.0 Marshmallow with CyanogenMod 13 ROM on your Moto device, first back up data and settings, make sure that your phone is rooted and install TWRP recovery.
After downloading the Marshmallow ROM and gapps zip files on your PC, connect your phone to your computer and copy these files to a separate folder which you’ll create on the internal storage. Then, disconnect the phone and boot it into recovery mode using Quick Boot app, which you can find on the Google Play store, but you can also manually boot, by following these steps: after shutting down the phone, press and hold, simultaneously, the volume down and power button, and when the display turns on, release them. Now, to highlight Recovery option, press the volume down button and to select it, use the Volume up button.
If your phone successfully boots into TWRP recovery, you won’t see any Android with exclamation mark. And now you can back up your data and settings by selecting the Backup button, then perform a Factory Reset from the main screen. You will tap on Wipe, then confirm the action by swiping from the bottom of the screen.
The next step is to go back to the TWRP main screen, and tap on Install, in order to install the ROM file. After selecting it, swipe from the bottom and you’ll begin flashing the update.
In the end, press the home button to get back to the main recovery screen, then install Gapps and restart your device by tapping the Reboot system button.