JOptionPane is not working with FlatLight or FlatDark Look and Feel

[FredKruse]

First of all, great work. I have integrated FlatLaf into my WritingTool project. My self-written dialogs work perfectly with FlatLaf. But when I open JOptionPane for short messages, error messages, etc., only the titles of the dialogs are displayed under Windows. Under Linux, the dialogs are so small that they are barely visible.
Is there a way (or a workaround) to get the JOptionPane methods to work?

[DevCharly]

Strange 😕

Works fine for me:

public class OptionPaneTest {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            FlatLightLaf.setup();
            JOptionPane.showMessageDialog( null, "Hello World" );
        });
    }
}

[FredKruse]

Thanks for the feedback. The example works for me too. Unfortunately, the same code doesn't work in the LibreOffice OXT that I'm programming. I have no idea what else I could try.

[DevCharly]

Also have no idea...

Did you use same JRE/JDK in both cases?
What JRE/JDK?

Runs your LibreOffice OXT only in LibreOffice?
Or also as stand-alone app?