WDM-KS is again very old technology (introduced in Win 98. I think, like DirectSound, it is emulated in current versions of Windows.
A long time ago, support for WDM-KS was enabled in Audacity, but at that time WDM-KS support in sound card drivers was frequently unstable, resulting in a surge of BSOD problems on some machines. If you are running a really old machine with a really old version of Windows, then I think Audacity 2.0.0 may have WDM-KS support enabled. In other cases, WDM or WASAPI with the current version of Audacity (2.3.0) is a better option.
Update: found this post - https://forum.audacityteam.org/t/providing-a-build-with-wdm-ks-support/39307/7