The following method of upgrading provides the cleanest transition between Devuan releases.
apt-get full-upgrade --autoremove --purge
The full-upgrade option allows packages to be removed as part of the upgrade process, meaning obselete packages in the new release may be removed.
The --autoremove command will also remove packaged that will be orphaned by the upgrade.
The --purge command will remove all the configuration files left behind for any package that is removed.