I didn't intend to suggest that you did, that's why there's a smiley at the end. You did suggest that I made my statements without checking their accuracy, I simply intended to suggest you apply the same standard to your own comments. My humour, such as it is, falling on deaf ears as so often the case

I didn't intend to suggest it was done by the update process either. It was almost certainly done by some action or interaction in the camera or gallery app. The camera app claimed to be using the SD card, but no new pictures were appearing in the gallery, and the camera app refused to take more than one picture unless closed and restarted.
File Manager showed files on the SD card, but as I said, Pictures and Video folders empty. I removed the SD card and verified on PC, then set a job to recover deleted files, which was looking to be fairly successful when I left it at 2am.

Camera operates normally when storing to internal memory, as expected.

Enough said. I'll carry on using my MX4 Ubuntu phone as workshop camera. Oddly it's one of only two apps on that device which isn't completely hateful.