From what I gather, keyboard errors are the first thing to happen after severe battery corrosion on 486 boards, since the the barrel resides just below the AT kb connector and above the controller on the majority of those motherboards, so checking for continuity in those areas should be of help. Also check the back of the board. Some ICs have a bit long pins that tend to short with each other causing all sorts of issues, had this happen once with a kb bios chip resulting to "keyboard not found" error.

I have the same board and the same problem. Gow to fix it?

Every possible answer is in this thread.

Pins 7 and 33 of HT6542 are shortened to ground. Pin 34 is wired to keyboard lock connector (pin 4 of 5, 5th is gnd). These pins is not shortened. Is it ok or not?

blacksn wrote on 2020-09-26, 09:43:

I have the same board and the same problem. Gow to fix it?

If you want to go hardcore, if you pull and upload an image of your bios it may be possible to patch the keylock check out of the bios.
I wonder if Artex ever got it working.

Bios is soldered into board. I cant boot OS to read rom and have no soldering station.