Fixes

src/Controls/src/Core/Compatibility/Handlers/Shell/Android/ShellToolbarTracker.cs

@@ -82,6 +82,7 @@ public ShellToolbarTracker(IShellContext shellContext, AToolbar toolbar, DrawerL
 			((IShellController)ShellContext.Shell).AddFlyoutBehaviorObserver(this);
 			ShellContext.Shell.Toolbar.PropertyChanged += OnToolbarPropertyChanged;
 			ShellContext.Shell.Navigated += OnShellNavigated;
+			ShellContext.Shell.PropertyChanged += HandleShellPropertyChanged;
 		}
 
 		void IShellToolbarTracker.SetToolbar(IToolbar toolbar)
@@ -182,6 +183,7 @@ protected override void Dispose(bool disposing)
 				((IShellController)ShellContext.Shell)?.RemoveFlyoutBehaviorObserver(this);
 				ShellContext.Shell.Toolbar.PropertyChanged -= OnToolbarPropertyChanged;
 				ShellContext.Shell.Navigated -= OnShellNavigated;
+				ShellContext.Shell.PropertyChanged -= HandleShellPropertyChanged;
 				UpdateTitleView(ShellContext.AndroidContext, _platformToolbar, null);
 
 				if (_searchView != null)
@@ -280,6 +282,12 @@ void OnShellNavigated(object sender, ShellNavigatedEventArgs e)
 			}
 		}
 
+		void HandleShellPropertyChanged(object sender, PropertyChangedEventArgs e)
+		{
+			if (e.Is(Shell.FlyoutIconProperty))
+				UpdateLeftBarButtonItem();
+		}
+
 		BackButtonBehavior _backButtonBehavior = null;
 		protected virtual void OnPagePropertyChanged(object sender, PropertyChangedEventArgs e)
 		{

src/Controls/src/Core/Compatibility/Handlers/Shell/iOS/ShellPageRendererTracker.cs

@@ -89,6 +89,8 @@ protected virtual void HandleShellPropertyChanged(object sender, PropertyChanged
 		{
 			if (e.Is(VisualElement.FlowDirectionProperty))
 				UpdateFlowDirection();
+			else if (e.Is(Shell.FlyoutIconProperty))
+				UpdateLeftToolbarItems();
 		}
 
 		protected virtual void OnBackButtonBehaviorPropertyChanged(object sender, PropertyChangedEventArgs e)

src/Controls/tests/TestCases.HostApp/Issues/Issue20166.cs

@@ -17,6 +17,7 @@ public Issue20166()
 		void Button1_Clicked(System.Object sender, System.EventArgs e)
 		{
 			CurrentItem = shellTab2;
+			Shell.FlyoutIcon = String.Empty;
 		}
 
 	}