Success! I went over to mac-usb-serial.com as Jim suggested, intending to send them email asking whether the Radioddity/QYT cable was likely supported. They had a button on their home page to download a serial detection app, and when I did that, it saw the cable immediately and gave me a link to the order page for the correct driver. Three minutes and $9.30 later, I was successfully retrieving data from my QB25. I exported it to a CSV file so I can peruse it in Excel. Thanks for the help, guys. If either of you are involved in CHIRP development, perhaps you can suggest that mac-usb-serial.com be mentioned on the MacOS Tips page. Their detection app makes it easy to tell whether you can get a compatible driver without all the trial and error of downloading other drivers. I still don't know what happened to the other 2-3 drivers I installed. They said "Installation successful" but I don't see them on my Mac.
73,Patty