Okay, I have made a new Microsoft account and the new OneDrive works as expected with rclone, so it would appear to be something 'different' with the old OneDrive.
For information, the old OneDrive works correctly, for all operations, with abraunegg's OneDrive Client for Linux. I don't know the precise history of this old OneDrive/Microsoft account – it's quite old and may even have started out as a TechNet account, though it is now just an ordinary personal account.
For me, I'll abandon the old OneDrive and call this fixed. I can get the uploaded files through the live.com web interface. Thanks to all who responded.