520 Custom Rom ((link)) — Nokia Lumia

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.

However, that does not mean you are stuck. The "Custom ROM" scene for the Lumia 520 is about , not OS replacement. Nokia Lumia 520 Custom Rom

If you want, I can:

If we have to pick a winner for the "Nokia Lumia 520 Custom Rom" that actually makes the phone useful, it is not Android nor Windows 10. This process permanently alters the device

This is the most headline-grabbing development. The Lumia 520, despite its age, can run full desktop Windows 10 — not Windows Mobile. However, the 520 is the absolute minimum spec. not OS replacement. If you want