The included startup scripts with the installer do not work on Ubuntu 18.04, and some of the examples available are more complex than necessary. The following simple systemd stanza will do the job just fine:
[Unit] Description=IBM Domino Server After=syslog.target network.target
Copy this file to /etc/systemd/system, and issue a systemctl daemon-reload command. Then enable the service using systemctl enable domino and start Domino 10 with systemctl start domino. Domino should automatically start on boot now, and the server log can be viewed by issuing systemctl status domino.