Thanks Dan. In the thread about OwnCloud https://community.nethserver.org/t/unistalling-owncloud/4078 it was suggested to remove other files including the database. Can I / should I do this by changing ‘owncloud’ to ‘nextcloud’?
yum remove owncloud nethserver-owncloud
rm -rf /var/www/html/owncloud
mysql -e "drop database owncloud;"