Requires Java 11. OpenJDK 11 recommended over Java SE.
Install Maven
Use Maven to fetch dependencies and build: mvn clean package
Built JAR should be something like target/qortal-1.0.jar
Create basic settings.json file: echo '{}' > settings.json
Run JAR in same working directory as settings.json: java -jar target/qortal-1.0.jar
Wrap in shell script, add JVM flags, redirection, backgrounding, etc. as necessary.
Or use supplied example shell script: run.sh