To successfully automate a VirtualBox VM to start at boot time, we must ensure we’re running VirtualBox version 5 and above.
By default, after installing VirtualBox, the vboxautostart-service unit file should exist in the /etc/systemd/system/ directory.
Alternatively, for systems missing the vboxautostart service, we can create a custom systemd unit file that will contain our configurations to run VirtualBox on boot. systemd is a system and service manager for most Linux-based OSes.
Didn’t see you mention the autostart-service, and the article is recent enough that maybe it was added as part of an update?