Hi thanks,
I’ve managed to dist upgrade from 16.04 to Ubuntu focal lts.
think my installation pre dates multi site, a mixed blessing
I found that my php was from a PPA and the upgrade broke that via Ubuntu managed to upgrade via PPA interestingly 127.0.0.1 loopback becomes localhost. And wrong user now reconfigured without any prompts
i kept going round in circles and after fixing things website health now shows path error.
config.php was the culprit a path to wp-content appeared, gedit and all is well 15 hours later.