If you want to use the phone as a dedicated offline MP3 player or a nightstand clock with Live Tiles, this is the most stable Nokia Lumia 520 Custom Rom available.
If you choose to modify your device, these are the standout hardware and software capabilities you can leverage: Nokia Lumia 520 Custom Rom
However, this is not an upgrade path for the average user. It is a challenging, risky, and often frustrating process that can permanently disable your device. The custom ROMs available are incomplete, unstable, and lacking in critical functionality like cellular connectivity. If you want to use the phone as
: Users can SSH into the device via USB, though some features like Wayland support remain untested. Windows 10 Mobile The custom ROMs available are incomplete, unstable, and
There is a "wow" factor to this one. Some developers have managed to boot on the Lumia 520 using ROMs like Resurrection Remix and CyanogenMod 14.1 . Videos from 2016 showed the phone booting into the modern Android interface, which was a jaw-dropping achievement at the time.