I've tried installing JabRef via the Ubuntu Software GUI (18.04). There are two jabref's listed in there: "jabref" (says Version 4.2-dev) and "JabRef" (Version 3.8.2+ds-3).
"JabRef" opens fine and seems to work, but the DOI search doesn't ("error while fetching from doi. invalid url")
"jabref" installs fine, but doesn't open when clicked.
Finally I downloaded the latest version from their website (JabRef-4.3.1.jar), sadly I get the following result:
bruno@bruno:~/Desktop/Jab$ java -jar JabRef-4.3.1.jar Error: Could not find or load main class org.jabref.JabRefMain Caused by: java.lang.NoClassDefFoundError: javafx/application/Application bruno@bruno:~/Desktop/Jab$
If I simply right-click on it and click "Open with OpenJDK 8 Java Runtime" or "Open with OpenJDK 11 Java Runtime", again nothing happens ... Does someone know a solution?