EDIT: ended up being 1 faulty ram stick, 1 (supposedly) bad psu, an overcooked cpu, a dead aio cooler and (potentially) a faulty psu. Thanks Linux bros.
I did the memtest. Figured out 1 out of 4 ram sticks are bad and sent it out on an RMA. Took the whole rig to a local shop and he load tested the PSU. It failed twice. He recommended I replace the PSU then the motherboard if I still had issues. So I replaced the PSU with a new unit, still the exact same issues. So I replaced the motherboard with a used one. Still the exact same issues. I updated the BIOS. Same issues but a new, more red Asus logo (yay).
I still cannot, for the love of AntiChrist, boot the thing. At. All. Not even from a usb. Attempting to fresh install windows and i have zero input from any devices.
I am at my wits end and I need my PC back up and running.
Linux bros blocked immediately.
...yes. since the first attempt over a month ago. Front ports. Motherboard ports. And i never plug a mouse or keyboard into my monitor or other usb hub.
I mean, something clearly isn't working right there, and I can't think of many things that would cause that.
considers
The keyboard (and mouse?) do work in the BIOS, just not in the Windows installer? While plugged into the port in question? (I mean, it's possible to disconnect the cable running from the USB header on the motherboard to the front panel.)
Have you tried, while the PC is on and the Windows installer is active, unplugging the keyboard and mouse and then re-plugging them back in? That'll reset the device and let the installer handle them. It's not completely impossible, I guess, that the BIOS talking to them could somehow put them in some kind of wonky state.
EDIT: If the keyboard and mouse aren't working in the BIOS either, try them on someone else's computer to rule them out as a source of trouble? I doubt that they are the problem, but might as well get the data point, just to be sure.