This guy took a lens off of an old WWI era folder and put is on an A7 III. The videos are really good.
Found this Youtube video. thought it interesting.
They tested the eye/face detect functions of the following cameras:
Canon EOS R, Fuji X-T3, Nikon Z6, Sony a9, Sony a7 III and Sony a6400
It is 20 minutes long, but if you scroll through the timeline bar, you'll see the thumbnails fear each...