I applied the update successfully today. At first the car wouldn't recognize the update on the USB stick, then I changed two things, one or the other of which might have been the secret:
1. Instead of not inserting the USB stick until going into "Settings --> Software Update..." as noted in the Electrek article, I inserted the USB stick first and then turned on just the infotainment system (using the button in the volume control knob).
2. I reformatted the USB stick from exFAT to FAT.
The update ran with the progress bar for about 12-13 minutes, then the radio screen went blank and nothing appeared to happen for quite some time. So then I turned the car on and I couldn't get Android Auto to work - the screen said "Can't connect to Android Auto - check your phone when safe".
I futzed about for a few minutes before deciding that hey - maybe I should actually check my phone. So I pulled the phone out of the charging slot so I could see the screen and reconnected it and Android Auto had reverted back to some of it's initial setup prompts that required acknowledgement. After going through those I reconnected and now everything works fine.
Thanks to the folks who've reported here what worked for them!