All's well when it ends well.
So, the RC and AC where both on and connected during the RC update.
The AC update lasted about 3 minutes with DJI Assistant, then again about 5 with DJIGO4.
The RC update lasted about 5 minutes.
Everything went smoothly, except for the slight scare I got when the RC started beeping.Oh, my device is a Sony Xperia XZ Premium, Android 8.0.0, not on DJI's list.
Good luck with your updates, folks!
A small disclosure, I expected it to fail but DJI came through with this one. Chapeau.
Not easy. DJI should have produced a video tutorial on how to update RC. I got mine going second attempt (does beep throughout!) . The secret in my view is to first download the firmware update. Then switch off everything and start again. Because you have now downloaded the software the program takes yo directly to upload to the RC which you have connected to your device with wifi NOT the OTG!
That's my ten pennies worth.