It's removed in qt6

src/kaddressbookmigrateapplication.cpp

@@ -3,8 +3,8 @@
 
    SPDX-License-Identifier: GPL-2.0-or-later
 */
-
 #include "kaddressbookmigrateapplication.h"
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
 
 #include <Kdelibs4ConfigMigrator>
 
@@ -64,3 +64,4 @@ void KAddressBookMigrateApplication::initializeMigrator()
 
     // TODO add folder to migrate
 }
+#endif

src/kaddressbookmigrateapplication.h

@@ -5,8 +5,9 @@
 */
 
 #pragma once
-
 #include "kaddressbook_export.h"
+#include <QObject>
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
 #include <PimCommon/MigrateApplicationFiles>
 
 class KADDRESSBOOK_EXPORT KAddressBookMigrateApplication
@@ -19,4 +20,4 @@ private:
     void initializeMigrator();
     PimCommon::MigrateApplicationFiles mMigrator;
 };
-
+#endif