The strange thing is that I did not deactivate automatic updates from anything.
The only way that I have managed to get automatic updates working is to:
1. Remove the filter define( ‘AUTOMATIC_UPDATER_DISABLED’, true ); from wp-config.php, a filter that I did not put there.
2. Delete Jetpack plug-in.
3. Install and activate Jetpack plug-in.
Then plug-in autoupdate works as expected.