SeaGlassLookAndFeel on Java 14

Question

Pluggable LookAndFeel was always risky (because the authors would move on), but SeaGlassLookAndFeel is so much prettier than the default that it seemed worth some risk and effort.

Now I'm trying to move our application to a newer version of Java (8 -> 14), and running into problems. Even after copying version 0.2.1 as described in Unable to use Sea Glass LAF for the Java application, I still get java.lang.NoClassDefFoundError: sun/swing/plaf/synth/SynthIcon.

Has anyone successfully used SeaGlassLookAndFeel on a recent Java?

My test application:

    import javax.swing.*;
    import java.awt.EventQueue;

    public class MainWindow extends JFrame {

        public MainWindow() {
            setTitle("SeaGlassLookAndFeel");
            setSize(300, 200);
            add(new JLabel("Hello, world!"));
            setVisible(true);
        }

        public static void main(String[] args)
        {
            EventQueue.invokeLater(() -> {
                try {
                    UIManager.setLookAndFeel("com.seaglasslookandfeel.SeaGlassLookAndFeel");
                    new MainWindow();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            });
        }

    }