[Milhouse]

Millhouse I presume this is a reply to me

Yes.

A column of text ran on startup, I presumed that was extraction, but too small and fast for me to read so no idea about errors. Can I capture this somehow if it happens again?

The only way to capture it is to take a photograph or video.

If the upgrade succeeds it will usually take 30-40 seconds to complete, showing progress messages (only about 8 lines) along the way, it will also confirm at the beginning that the extraction is taking place. If the upgrade fails it should show a message and reboot after 30 seconds. It should be very obvious whether the upgrade is being attempted or not.

A column of text sounds like a regular (non-upgrade) boot when you don't have "quiet" added to the end of your line in cmdline.txt.