protected boolean isIndeterminateStateSupported() {
		LookAndFeel laf = UIManager.getLookAndFeel();
		return laf instanceof FlatLaf || laf.getClass().getName().equals( "com.apple.laf.AquaLookAndFeel" );
	}
Returns whether the current LaF supports displaying the indeterminate state.
Returns {@code true} for FlatLaf and macOS Aqua.
flatlaf-extras/src/main/java/com/formdev/flatlaf/extras/components/FlatTriStateCheckBox.java