configure main and universe repo in sources.list, install dialog utility
usl-mm-bionic-upgrade ->
replace current release codename with codename in first argument, upgrade LXD to 4.0 SNAP version, upgrade system, replace some lines in /root/onstart, reboot
replace current release codename with codename in first argument, upgrade LXD to 4.16 SNAP version, upgrade system, replace some lines in /root/onstart, reboot