Flashing OpenWRT onto an Ubiquiti EdgeRouter Pro ER-8 ERPro-8 ubnt_200

Hi There,

I have an EdgeRouter Pro and I want to flash OpenWRT on it. There is a guide available to boot the board from the USB port but this is something I really don't want as a permanent solution, furthermore, it needs manual intervention every time you want to boot it from USB.

I've come across this info when searching for a solution:

Any help is appreciated.