With tomcat11, vnu webapp is reachable at:

  http://localhost:8080/vnu

On some architectures (eg. i386, loong64), you may also have to launch
tomcat with the following JVM option "-Xss2048k".

To achieve this, you could set the CATALINA_OPTS environment variable this way.
  echo -e '[Service]\nEnvironment="CATALINA_OPTS=-Xss2048k"' | \
    systemctl edit --drop-in vnu-tomcat11.conf --stdin tomcat11.service

Then restart the service:

  systemctl restart tomcat11