Following exactly the method here: https://edgeup.asus.com/2021/guide-how-to-enable-resizable-bar-on-your-asus-powered-gaming-pc/
1) Latest bio for Z490I installed (2005)
2) GPU (EVGA 3080) updated to latest bios per mfr tool
3) GPU vBIOS updated to latest version per mfr tool
4) Verified that partition is GPT in disk management (plus, UEFI bios was already in-use and CSM already disabled)
The, the only step left is to set "Re-size BAR Support" from DISABLED to AUTO.
Prior to this setting, everything boots fine and the system is nominal. The moment that ONLY that setting is changed and a save+reset is done from bios, the bios fails POST and sits with a black screen. I'm unable to plug into the motherboard HDMI due to my case blocking it (lol) so I can't verify that video output there functions, however even when holding down the power button on the case, the system does not even power off, suggesting to me that it is in a stuck state.
I am unable to recover the system until I perform bios flashback to reset all settings (jumper would probably work but I dont want to reopen the small ITX case...
When trying a fresh bios, the same result occurs.