`include-shadow` defaults to `true` so this isn't a breaking change

src/plugins/screenshot/org.kde.KWin.ScreenShot2.xml

@@ -39,7 +39,7 @@
             * "include-decoration" (b): Whether the decoration should be included.
                                         Defaults to false
             * "include-shadow" (b): Whether the shadow should be included.
-                                    Defaults to false
+                                    Defaults to true
             * "native-resolution" (b): Whether the screenshot should be in
                                        native size. Defaults to false
 
@@ -89,7 +89,7 @@
             * "include-decoration" (b): Whether the decoration should be included.
                                         Defaults to false
             * "include-shadow" (b): Whether the shadow should be included.
-                                    Defaults to false
+                                    Defaults to true
             * "native-resolution" (b): Whether the screenshot should be in
                                        native size. Defaults to false
 
@@ -273,7 +273,7 @@
             * "include-decoration" (b): Whether the decoration should be included.
                                         Defaults to false
             * "include-shadow" (b): Whether the shadow should be included.
-                                    Defaults to false
+                                    Defaults to true
             * "native-resolution" (b): Whether the screenshot should be in
                                        native size. Defaults to false
 

src/plugins/screenshot/screenshotdbusinterface2.cpp

@@ -107,7 +107,7 @@ static ScreenShotFlags screenShotFlagsFromOptions(const QVariantMap &options)
         flags |= ScreenShotIncludeDecoration;
     }
 
-    const QVariant includeShadow = options.value(QStringLiteral("include-shadow"));
+    const QVariant includeShadow = options.value(QStringLiteral("include-shadow"), true);
     if (includeShadow.toBool()) {
         flags |= ScreenShotIncludeShadow;
     }