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.
no matter what i do, i can't get rid of it(igpu). it always shows up in on afterburner and in devices.. disabled, and uninstalled... still pops up in ab and device manager. it's like that itch that won't go away after a night of drinking and you wake up in a ditch with your pants around your ankles and you wonder how you got there..

Intel CPU with iGPU usually show the same behaviour. It uses the iGPU with an attached display and when it senses a dGPU with a display it will switch to that but you will probably still see the iGPU in device manager. This is from memory as I have not used and Intel for a long time.
I haven't had the same problem with intel... intel i can disable the igpu in the bios. even with the 5x00 series amd igpu i can disable the igpu, just not with the 7xxx igpu. one thing i've noticed with the amd 7xxx series igpu, is that if you have a discrete AMD gpu (6xxx/5xxx gpu) is that the igpu attaches itself to the discrete gpu and runs in a hybrid mode. doesn't happen with nvidia disrete gpu, though the amd igpu will still show up on af and control panel. I'm sure eventually AMD and the board manufacturers will allow me to disable it.