#1:

I've seen reports that a PC or PC XT keyboard (not a PS/2 or AT, however) can be used by constructing an adapter.

Note that you'll need a voltage regulator (an LM7805 will work) to drop the +12 to +5.

The scancodes are the same, but the initial conversation is a bit different, so I don't know if it will work.

#2:

Try it with an adapter, but the BIOS selftest also includes the keyboard controller, so hopely the 3rd party keyboard will not fail. Otherwise, sometimes there are single M24 keyboards on eBay & Co. You also can use the keyboard of M240.

The voltage regulator in the adapter is important, as the M24 keyboard connector supplies +12V.