OK here’s the lowdown on USB Vs PS/2 keyboards …
On a PC, the first thing to happen after you switch it on is the BIOS (contained on a chip on the motherboard) performs a self test and initialises the hardware.
In older PC’s the BIOS could initialise ONLY PS/2 keyboards and mice … if you had a USB KB or mouse the drivers could ONLY be loaded when the operating system had been loaded from the hard drive … in other words, the BIOS had no idea what a USB KB or mouse was, the OS loaded the drivers … which meant that USB keyboards could NOT access the BIOS, or do ANYTHING before the drivers were loaded.
later BIOS’s WERE able to initialise USB keyboards, but this function wasn’t enabled by default … so you would initially require a PS/2 KB to access the BIOS and turn support for USB keyboards ON.
still more recent PC’s have this feature enabled by default … so USB keyboards are OK from the getgo
and indeed VERY recent PC’s may not have a PS/2 port at all.
If on the other hand a PS/2 port is present … it is pretty much always active and immediately available.
So if NO PS/2 keyboard is working (ie. you cannot access the BIOS with it), it’s likely the PS/2 controller/port is broken, or the BIOS is corrupt.
In summary, if you cannot use a PS/2 keyboard to access the BIOS … it is more than likely a hardware issue, and nothing to do with the OS.
Try removing the mains plug from the wall … whilst the plug is removed, hit the power button to discharge any power left in the power supply … plug back in, and try again.
If that doesn’t work, you’ll want to try a BIOS reset.
and if that doesn’t work … try a USB keyboard, and hope that it’s recognised.
But you REALLY want to be testing this with a wired keyboard … wireless introduces other failure points that just confuse the diagnostic process.