Index: core/src/org/openstreetmap/josm/gui/MainApplication.java
===================================================================
--- core/src/org/openstreetmap/josm/gui/MainApplication.java	(revision 17791)
+++ core/src/org/openstreetmap/josm/gui/MainApplication.java	(working copy)
@@ -903,6 +903,7 @@
         }
         // Configure Look and feel before showing SplashScreen (#19290)
         setupUIManager();
+        SwingUtilities.updateComponentTreeUI(mainFrame);
 
         final SplashScreen splash = GuiHelper.runInEDTAndWaitAndReturn(SplashScreen::new);
         // splash can be null sometimes on Linux, in this case try to load JOSM silently