WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.freeplane.launcher.Launcher (file:/usr/share/freeplane/freeplanelauncher.jar) to field sun.awt.X11.XToolkit.awtAppClassName
WARNING: Please consider reporting this to the maintainers of org.freeplane.launcher.Launcher
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
I haven't found a workaround so far except for disabling this warning.