@SpiceWeasel
Most Asus boards with USB BFB accept mod files (M5E.CAP), this is the prefered way to flash, you can read more here:
[Guide] How to flash a modded AMI UEFI BIOS - BIOS/UEFI Modding / BIOS Modding Guides and Problems - Win-Raid Forum (level1techs.com)