A DESCRIPTION OF THE PROBLEM :
I tested Font.loadFont() for JetBrains Mono font (https://fonts.google.com/specimen/JetBrains+Mono) and Ubuntu font (https://fonts.google.com/specimen/Ubuntu). When I load light/thin fonts then for these fonts distinct families are created. For example, this is a piece of `System.out.println(javafx.scene.text.Font.getFamilies())` command: JetBrains Mono NL, JetBrains Mono NL Light, JetBrains Mono NL Thin, .... Ubuntu, Ubuntu Condensed, Ubuntu Light, Ubuntu Mono, Ubuntu Thin

The reason why I say it is a bug because `-fx-font-weight: 300` doesn't work. It is necessary to use `-fx-font-family: 'Ubuntu Light';-fx-font-weight: normal;` to make font lighter. And this contradicts the specification (https://openjfx.io/javadoc/23/javafx.graphics/javafx/scene/doc-files/cssref.html#typefont) , where it is stated:
<font-weight> The font's weight, using the following syntax:
[ normal | bold | bolder | lighter | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900 ]

So, no `lighter`, no `100`, `200`, `300` will work.




---------- BEGIN SOURCE ----------
public class JavaFxTest10 extends Application {

    @Override
    public void start(Stage primaryStage) {
        var fonts = List.of(
                "JetBrainsMonoNL-Bold.ttf",
                "JetBrainsMonoNL-BoldItalic.ttf",
                "JetBrainsMonoNL-Regular.ttf",
                "JetBrainsMonoNL-Light.ttf",
                "JetBrainsMonoNL-LightItalic.ttf",
                "JetBrainsMonoNL-Thin.ttf",
                "JetBrainsMonoNL-ThinItalic.ttf");
        fonts.forEach(f -> Font.loadFont(JavaFxTest10.class.getResource(f).toExternalForm(), 10));
        System.out.println(javafx.scene.text.Font.getFamilies());

        var label1 = new Label("Some text");
        label1.setStyle("-fx-font-family: 'JetBrains Mono NL';-fx-font-weight: normal;");//OK
        var label2 = new Label("Some text");
        label2.setStyle("-fx-font-family: 'JetBrains Mono NL';-fx-font-weight: 100;");//NOT OK
        var label3 = new Label("Some text");
        label3.setStyle("-fx-font-family: 'JetBrains Mono NL Thin';-fx-font-weight: normal;");//OK
        var root = new VBox(label1, label2, label3);
        root.setStyle("-fx-font-size: 18px");
        Scene scene = new Scene(root, 400, 200);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}
---------- END SOURCE ----------

FREQUENCY : always