Ubuntu 18.04.2 build of Tomcat 9 not writing to catalina.out, but in systemd status
You need to edit the file: /lib/systemd/system/tomcat9.service
Comment out the line: SyslogIdentifier=tomcat9
and add these two lines:
StandardOutput=append:/var/log/tomcat9/catalina.out
StandardError=append:/var/log/tomcat9/catalina.out