[iOS] Fix Navigation Page BackButtonTitle Not Updating

src/Controls/src/Core/Compatibility/Handlers/NavigationPage/iOS/NavigationRenderer.cs

@@ -1422,6 +1422,8 @@ void HandleChildPropertyChanged(object sender, PropertyChangedEventArgs e)
 				else if (e.PropertyName == NavigationPage.TitleIconImageSourceProperty.PropertyName ||
 					 e.PropertyName == NavigationPage.TitleViewProperty.PropertyName)
 					UpdateTitleArea(Child);
+				else if (e.PropertyName == NavigationPage.BackButtonTitleProperty.PropertyName)
+					UpdateBackButtonTitle(Child);
 				else if (e.PropertyName == NavigationPage.IconColorProperty.PropertyName)
 					UpdateIconColor();
 			}

src/Controls/tests/TestCases.HostApp/Issues/Issue31539.cs

@@ -0,0 +1,70 @@
+using System.Collections.ObjectModel;
+
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 31539, "[iOS, macOS] Navigation Page BackButtonTitle Not Updating", PlatformAffected.iOS | PlatformAffected.macOS)]
+
+public class Issue31539 : TestNavigationPage
+{
+	protected override void Init()
+	{
+		Navigation.PushAsync(new Issue31539ContentPage());
+	}
+}
+
+public class Issue31539ContentPage : ContentPage
+{
+	public Issue31539ContentPage()
+	{
+		var layout = new VerticalStackLayout
+		{
+			Padding = 20,
+			Spacing = 12
+		};
+
+		var pushButton = new Button
+		{
+			Text = "Push Second Page",
+			AutomationId = "PushSecondPage"
+		};
+		pushButton.Clicked += OnPushSecondPage;
+
+		var backTitleButton = new Button
+		{
+			Text = "Set BackButtonTitle = 'Back Home'",
+			AutomationId = "SetBackButtonTitle"
+		};
+		backTitleButton.Clicked += OnSetBackButtonTitle;
+
+		layout.Children.Add(pushButton);
+		layout.Children.Add(backTitleButton);
+
+		Content = layout;
+	}
+
+	void OnPushSecondPage(object sender, EventArgs e)
+	{
+		Navigation.PushAsync(new Issue31539SecondContentPage());
+	}
+
+	void OnSetBackButtonTitle(object sender, EventArgs e)
+	{
+		NavigationPage.SetBackButtonTitle(this, "Back Home");
+	}
+}
+
+public class Issue31539SecondContentPage : ContentPage
+{
+	public Issue31539SecondContentPage()
+	{
+		Content = new StackLayout
+		{
+			Padding = 20,
+			Spacing = 12,
+			Children =
+			{
+				new Label { Text = "This is the second page.", AutomationId = "SecondPageLabel" }
+			}
+		};
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue31539.cs

@@ -0,0 +1,27 @@
+# if TEST_FAILS_ON_ANDROID && TEST_FAILS_ON_WINDOWS    // BackButtonTitle is only applicable for iOS and macOS
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+	public class Issue31539 : _IssuesUITest
+	{
+		public Issue31539(TestDevice device) : base(device) { }
+
+		public override string Issue => "[iOS, macOS] Navigation Page BackButtonTitle Not Updating";
+		[Test]
+		[Category(UITestCategories.Navigation)]
+		public void VerifyBackButtonTitleUpdates()
+		{
+			App.WaitForElement("PushSecondPage");
+			App.Tap("PushSecondPage");
+			App.TapBackArrow();
+			App.Tap("SetBackButtonTitle");
+			App.Tap("PushSecondPage");
+			App.WaitForElement("SecondPageLabel");
+			VerifyScreenshot();
+		}
+	}
+}
+#endif