I basically have the same setup as you and have had this issue. It certainly seems odd, but what works for me is when I turn the PC on I wait 1 second and then turn the monitor on. The monitor seems to recognize the PC and I can see the BIOS prompt. Hope this helps.
Looks like a issue with asus monitors and displayport 1.4 as I also have this same issue with the tuf gaming vg28uql1a as I have 2 lg monitors that are displayport 1.2 and they work fine. All asus support does is request me to do an rma which I did and still same issue. Happening on a rog xiii hero and a 3080ti
Yes. It seems nothing is that consistent after messing with options more. The 10 second POST thing does nothing for me actually. The only real way I can get into BIOS via HDMI is from a fresh power on with turning the monitor on after 1 second. Otherwise, I connect the DP cable to the motherboard and that works every time.
Not that I care to enter the BIOS all the time, just would be nice to have the monitor respond quickly. It just takes forever to recognize a signal. Even from waking the PC up and the monitor on idle.
I am on V023 for firmware as I can't seem to update it to 024. Maybe 024 is a little better at some of these things.