Asrock 670E Steel legend that i have my 7700X doesn't have any options for display.
And neither does the Asrock 670E Taichi... maybe it's just an asrock thing. I normally go with Asus boards.
It's not an ASRock thing. All suffer from the introduction of AM5 socket and chips. Keep an eye out for BIOS updates the next couple of months as they will come as it is a brand new platform.
Asrock just released bios update (1.11) that now gives you the ability to boot from internal(igpu) or external display... but still no option to disable igpu
Maybe power management got smarter and can detect if/when the iGPU is not being used. It shouldn't be difficult for zen4 CPUs because the
iGPU is only to "light up a display" according to AMD CEO. Just speculating.