Hello @somebody and welcome to the Cloudron forum
There is no need for a custom crontab or bash script.
See https://help.ubuntu.com/community/AutomaticSecurityUpdates
You can edit /etc/apt/apt.conf.d/50unattended-upgrades and enable the automatic reboot:
- //Unattended-Upgrade::Automatic-Reboot "false";
+ Unattended-Upgrade::Automatic-Reboot "true";
and just to be sure restart the service with:
systemctl restart unattended-upgrades.service
With this change the system should automatically reboot.
