diff -Naur konsole-21.08.0.orig/src/MainWindow.cpp konsole-21.08.0.new/src/MainWindow.cpp
--- konsole-21.08.0.orig/src/MainWindow.cpp	2021-08-04 18:48:59.000000000 -0300
+++ konsole-21.08.0.new/src/MainWindow.cpp	2021-08-18 00:11:52.801474543 -0300
@@ -56,6 +56,8 @@
 #include "terminalDisplay/TerminalDisplay.h"
 #include "widgets/ViewContainer.h"
 
+#include <konsoledebug.h>
+
 using namespace Konsole;
 
 MainWindow::MainWindow() :
@@ -103,7 +105,7 @@
 
     // create view manager
     _viewManager = new ViewManager(this, actionCollection());
-    connect(_viewManager, &Konsole::ViewManager::empty, this, &Konsole::MainWindow::close);
+    connect(_viewManager, &Konsole::ViewManager::empty, this, &QWidget::close);
     connect(_viewManager, &Konsole::ViewManager::activeViewChanged, this,
             &Konsole::MainWindow::activeViewChanged);
     connect(_viewManager, &Konsole::ViewManager::unplugController, this,
@@ -129,8 +131,10 @@
     // in terminal applications
     KAcceleratorManager::setNoAccel(menuBar());
 
-    // create menus
-    createGUI();
+    constexpr KXmlGuiWindow::StandardWindowOptions guiOpts = ToolBar | Keys | Save | Create;
+    const QString xmlFile = componentName() + QLatin1String("ui.rc"); // Typically "konsoleui.rc"
+    // The "Create" flag will make it call createGUI()
+    setupGUI(guiOpts, xmlFile);
 
     // remember the original menu accelerators for later use
     rememberMenuAccelerators();
@@ -889,7 +893,15 @@
 #if KWINDOWSYSTEM_VERSION < QT_VERSION_CHECK(5,82,0)
         KWindowEffects::enableBlurBehind(winId(), blur);
 #else
-        KWindowEffects::enableBlurBehind(windowHandle(), blur);
+        // Set the WA_NativeWindow attribute to force the creation of the QWindow.
+        // Without this QWidget::windowHandle() returns 0.
+        // See https://phabricator.kde.org/D23108
+        setAttribute(Qt::WA_NativeWindow);
+        if (QWindow *window = windowHandle()) {
+            KWindowEffects::enableBlurBehind(window, blur);
+        } else {
+            qCWarning(KonsoleDebug) << "Blur effect couldn't be enabled.";
+        }
 #endif
     }
 }
@@ -935,9 +947,14 @@
         menuBar()->setVisible(_menuBarInitialVisibility);
         _toggleMenuBarAction->setChecked(_menuBarInitialVisibility);
         _menuBarInitialVisibilityApplied = true;
-        if (!KonsoleSettings::saveGeometryOnExit()) {
-            resize(sizeHint());
-        }
+    }
+
+    if (!KonsoleSettings::saveGeometryOnExit()) {
+        // Delay resizing to here, so that the other parts of the UI
+        // (ViewManager, TabbedViewContainer, TerminalDisplay ... etc)
+        // have been created and TabbedViewContainer::sizeHint() returns
+        // a usuable size.
+        resize(sizeHint());
     }
 
     // Call parent method