Thank you Neil. I removed the 2nd line and L&F is installed OK. But the Options ribbon remains white. The FlatLaf module was already a dependency.
FYI I submitted an issue on the FlatLaf GitHub as well. Le lundi 15 novembre 2021, 23:43:23 UTC+1, Neil C Smith <neilcsm...@apache.org> a écrit : On Mon, 15 Nov 2021, 21:15 Jerome Lelasseux, <lelass...@yahoo.com> wrote: Sorry I meant FlatLaf Dark. I use the following in ModuleInstall::validate() NbPreferences.root().node("laf").put("laf", "com.formdev.flatlaf.FlatDarkLaf"); UIManager.installLookAndFeel(new UIManager.LookAndFeelInfo("FlatLaf Dark", FlatDarkLaf.class.getName())); Try removing the second line. Leave the FlatLaf module to install the look and feel. If that's not enough also add dependencies in that module on the FlatLaf modules. See eg. https://github.com/praxis-live/praxis-live/blob/master/praxis.live.laf/src/org/praxislive/ide/laf/Installer.java#L47 This works fine for me. Best wishes, Neil