UnattendedUpgrades
UnattendedUpgrades should include all added repositories (rspam, sury php and GoAccess) if used. Currently only sure php is added to the config file.
Besides Unattended-Upgrade::Mail "root"; should be set as of the recommendation of the Debian Wiki.
codename=${distro_codename}-updates is also added as repository, because it doesn't harm if it is not part of sources.list and it should be used if it is there.
Putting the data in /etc/apt/apt.conf.d/51unattended-upgrades instead of 50unattended-upgrades avoids problems during updates.
The attached merge request modifies the behavior of the Autoinstaller as described.
P.S.: unattended-upgrade -d --dry-run allows to verify that the config files 50unattended-upgrades and 51unattended-upgrades are both read.