A popup window may close immediately after it appears in Linux if a submenu item has been clicked before.

To reproduce use the attached FocusableNestedMenu.java.
        // To reproduce manually
        // 0. set automated to false and run the test
        // 1. right click on the frame
        // 2. select "sub menu title" submenu
        // 3. click on the item
        // 4. try to open the menu again by right clicking on the frame
        // it will disappear immediately, but if you press the right button and then
        // away from the menu and release the button there, the menu will
        // stay on the screen.

This only happens on Linux, both X11 and XWayland are affected.
For some reason the mouseReleased event is passed to the BasicMenuUI handler for a newly opened popup menu, it calls manager.clearSelectedPath(); which causes the popup menu to be dismissed.

https://github.com/openjdk/jdk/blob/644d154c7c771236904560fc5b91f149a6a646cf/src/java.desktop/share/classes/javax/swing/plaf/basic/BasicMenuUI.java#L551

Applying the following patch solves the issue, and from the testing, nothing seems to be broken, but it should be tested more thoroughly

--- a/src/java.desktop/share/classes/javax/swing/plaf/basic/BasicMenuUI.java
+++ b/src/java.desktop/share/classes/javax/swing/plaf/basic/BasicMenuUI.java
@@ -25,6 +25,7 @@
 
 package javax.swing.plaf.basic;
 
+import jdk.internal.util.OperatingSystem;
 import sun.swing.DefaultLookup;
 import sun.swing.UIAction;
 import java.awt.*;
@@ -547,8 +548,9 @@ public void mouseReleased(MouseEvent e) {
             MenuSelectionManager manager =
                 MenuSelectionManager.defaultManager();
             manager.processMouseEvent(e);
- if (!e.isConsumed())
+ if (!e.isConsumed() && !OperatingSystem.isLinux()) {
                 manager.clearSelectedPath();
+ }
         }
 
         /**