This is one of those problems where I know I've proceeded from a false assumption, I've built a bunch of crap around it, now something's changed and broken stuff, and it's pissing me off. I have a ...

A new security feature in Apple’s upcoming macOS 13 Ventura will automatically block new USB-C devices from communicating with the operating system until the accessory can be approved by the user.

My P4P800 won't boot from my USB stick when Legacy USB Support is turned on; maybe that's worth a shot.