Index: ivy.xml
===================================================================
--- ivy.xml	(revision 16222)
+++ ivy.xml	(working copy)
@@ -26,6 +26,7 @@
         <dependency org="org.tukaani" name="xz" rev="1.8" conf="api->default"/>
         <dependency org="com.drewnoakes" name="metadata-extractor" rev="2.13.0" conf="api->default"/>
         <dependency org="ch.poole" name="OpeningHoursParser" rev="0.21.1" conf="api->default"/>
+        <dependency org="com.formdev" name="flatlaf" rev="0.29" conf="api->default"/>
         <!-- sources->sources -->
         <dependency org="org.openstreetmap.jmapviewer" name="jmapviewer" rev="2.13" conf="sources->sources"/>
         <dependency org="javax.json" name="javax.json-api" rev="1.1.4" conf="sources->sources"/>
@@ -36,5 +37,6 @@
         <dependency org="org.tukaani" name="xz" rev="1.8" conf="sources->sources"/>
         <dependency org="com.drewnoakes" name="metadata-extractor" rev="2.13.0" conf="sources->sources"/>
         <dependency org="ch.poole" name="OpeningHoursParser" rev="0.21.1" conf="sources->sources"/>
+        <dependency org="com.formdev" name="flatlaf" rev="0.29" conf="sources->sources"/>
     </dependencies>
 </ivy-module>
Index: src/org/openstreetmap/josm/gui/MainApplication.java
===================================================================
--- src/org/openstreetmap/josm/gui/MainApplication.java	(revision 16222)
+++ src/org/openstreetmap/josm/gui/MainApplication.java	(working copy)
@@ -164,6 +164,9 @@
 import org.openstreetmap.josm.tools.bugreport.BugReportSender;
 import org.xml.sax.SAXException;
 
+import com.formdev.flatlaf.FlatDarkLaf;
+import com.formdev.flatlaf.FlatLightLaf;
+
 /**
  * Main window class application.
  *
@@ -1048,6 +1051,9 @@
     }
 
     static void setupUIManager() {
+        UIManager.installLookAndFeel("FlatLaf Light", FlatLightLaf.class.getName());
+        UIManager.installLookAndFeel("FlatLaf Dark", FlatDarkLaf.class.getName());
+
         String defaultlaf = PlatformManager.getPlatform().getDefaultStyle();
         String laf = LafPreference.LAF.get();
         try {