No Stereo Mix Input in brand new MS Surface Pro 6?

Question

I require stereo mix input for my work (use of Audacity, Goldwave and Sound Forge). It is not disabled. It is simply not there. Have downloaded audio drivers from Realtek and via W10 Update, no change. This is a $1500 laptop/tablet I just bought, 7/6/2019, and no stereo mix input? My $300 Dell was fully functional, including Stereo Mix. This is beyond frustrating.

I've tried two workarounds, ActivePresenter and Voicemeeter, and neither work. Did anyone have any success who can share?

Thanks in advance. I have 5 days left to return this laptop within the return period. Hoping for some good news from this awesome group...