Well it looks like you are able to flash your Radeon RX 480 to an RX 580. A user on the TechPowerUp forums successfully flashed his XFX RX 480 with a BIOS from a Sapphire RX 580 Limited Edition. The user obtained the BIOS and then used ATIFlash to complete the process. The XFX RX 480 did have a dual-BIOS and this is something you might want to consider when doing any type of GPU BIOS flashing.
- Computex 2018