Hello Tom69 & Dave,
I don't have access to a Yeti Blue, so can't test properly. All other recording devices I've used, with correct PC, mic & ADR settings, appear as stereo tracks in ADR.
To try to track down possible causes of your issue, I've tested recordings using Audio-M Producer (mic) & Microsoft G433 Gaming Headset) on multiple PCs, different versions of ADR & Audacity. Unfortunately, I got the same results each time - audio recorded on both channels.
It's not hard to find (Dr Google) other examples of people having similare issues, though not necessarily with ADR or Yeti Blue.
Have you tested your Yeti using a different PC or another recording application (like Audacity)? That might help narrow the possible causes.
PIX
PIX YouTube channel