Comment # 13 on bug 1230115 from Takashi Iwai

Please don't use yast2-sound.  It's an obsoleted stuff and has been dropped
already from TW.  It just breaks things on modern systems, and you made it. 
One can use yast2-sound only if one know exactly what it really does.

So, scratch the setup it made.  It likely made some configuration in
/etc/modprobe.d/*.

Then install the latest sof-firmware package from OBS multimedia:libs repo
  http://download.opensuse.org/repositories/multimedia:/libs/15.6/
and retest.  The sof-firmware package of the current Leap 15.6 might be too old
for the newer kernels.

I'm going to submit sof-firmware update for Leap 15.6 later, but basically it's
same from what you get from the OBS repo above.