Warning: This process permanently alters the device. It is intended for advanced users. You can brick your phone (turn it into a paperweight) if you make a mistake.

Option C: The "Android" Myth

You may find old, abandoned projects (like a port of Android 4.4 KitKat) created by developers years ago.

Flashing a custom ROM on the Lumia 520 is largely done for nostalgia or as an engineering hobby rather than for daily use.

CyanogenMod 13: Based on Android 6.0.1; one of the most popular builds for this hardware.

Benefits:

Limitations and risks