jpackage is garbage for .rpm and .deb and seems like "they" dont care, see https://bugs.openjdk.org/browse/JDK-8208405

IMHO jpackage is absolutely useless for java applications, as .deb and .rpm already have such a nice and good deps management. It would be so easy to modify the control file (e.g. for .deb) to add "default-jre" as dependency for that app. That would save me about 85% of my applications size. Its a joke...

The only useful thing at the moment is to use jpackage to create a rpm and deb, then extract those and get the files used as templates and modify them for your needs. Then use the native tools needed to create rpm/deb.