Basically a combination of Installing Mirth on Ubuntu - A How To and Run Mirth service manually works, running from systemd errs with "No suitable JVM...".
This will create a Mirth Connect 4.5.0 service for a user and group mirth running on OpenJDK 21.
- Install JRE:
sudo apt install openjdk-21-jre-headless
- Create user mirth:
sudo adduser mirth