Comment # 1 on bug 1088286 from Takashi Iwai

Could you give the hardware details?  Such a problem is very much depending on
the hardware, so without the information, we can't help at all.

If the installer works, you can try to boot a recovery boot from the installer,
and check whether the keyboard works.
If it's OK, try to run hwinfo and save it, and upload to this Bugzilla.

Alternatively, if Leap 42.3 installation (or TW installation) works on this
machine, install Leap 42.3 or TW at first, then install Leap 15.0 kernel on top
of it.  In this way, we can see whether it's a kernel problem or something
else.