[raverbashing]

I wonder if we have confirmation from an M1 owner (that is familiar with Apple stuff) that there's no way of booting from external media from the "bios"

Of course, then you would need to get on the whole trouble of initializing video/T2/etc but it could be doable

[kitsunesoba]

I don't own an M1 device, but it's been confirmed that boot security can be disabled entirely. I'm pretty sure that booting from external devices works fine once security has been disabled.

It's a bit different from Intel based Macs though. It used to be you'd hold Option while booting to be presented with an EFI boot disk picker, but now you hold down the power button to be greeted by a micro-macOS boot options menu.