I haven't read every reply but I've read the entire opening post. My guess is that yanking the GPU out of the pcie slot has caused damage to the mobo in a way that is affecting both pcie slots.
The only other thing it could be is graphics drivers but if you done a completely fresh install of win10 and GPU drivers then it can't be that. Just for the sake of thoroughness you could try another fresh win10 install followed by an even older graphics driver version but I doubt it will work since you already tried a previously-working driver version and that didn't fix it.
Yeah I thought that, so I have another asus x570-p (same mobo) on the way to see if it fixes it.
A few people have said though if there was damage I'd get BSODs or much worse issues. But it does seem quite suspect that this was noticed RIGHT after I took/yanked out the 3080ti and put in the 3070ti... Or else I never would have sold the 3080ti to someone.
Some guys on another thread seem to think it's because I updated the mobo bios from Windows using asus EZ flash, as that's something you should never ever do apparently.
I always thought the bios was only responsible for exactly that though - the basic checks during post before it hands everything over to windows.
But guys here know their stuff. Flashing the bios again now (from the bios) as we speak.