> iBoot is the main bootloader on M1 machines. It is small. It cannot understand external storage. It does not support USB. It does not have a UI. All it can do is boot from internal storage, and show an Apple logo, a progress bar, and a few error messages.
IIRC he’s said before that iBoot doesn’t even have keyboard support; it can tell if you’re holding down the power button to enter recovery mode, but that’s it. There is no workaround for this; it is not possible to boot over USB if the bootloader does not speak USB.