Thanks Fang! Your article got me to the solution. Looks like it was slightly updated. I have a Macbook Air with the Apple M2 chip. I had to open FaceTime and Quicktime Player, then a little Camera icon showed up on the top menu tray, then within it was a dropdown menu 'FaceTime HD Camera', and there I was able to choose Portrait. Now I can record with QuickTime player and the background is blurred.