It was fixed in 5.13.0beta2

CMakeLists.txt

@@ -63,12 +63,7 @@ configure_file(config-akonadi-search.h.in ${CMAKE_CURRENT_BINARY_DIR}/src/config
 find_package(KF5DesignerPlugin ${KF5_MIN_VERSION} CONFIG)
 set_package_properties(KF5DesignerPlugin PROPERTIES DESCRIPTION "KF5 designer plugin" TYPE OPTIONAL)
 
-# workaround for https://bugreports.qt.io/browse/QTBUG-74665 (bug in qt5.13 reevaluate it)
-if (${Qt5Widgets_VERSION} STREQUAL "5.13.0")
-   MESSAGE(STATUS "Qt version: ${Qt5Widgets_VERSION} DISABLE compile without deprecated methods. bug QTBUG-74665")
-else()
-   add_definitions(-DQT_DISABLE_DEPRECATED_BEFORE=0x060000)
-endif()
+add_definitions(-DQT_DISABLE_DEPRECATED_BEFORE=0x060000)
 add_definitions(-DQT_NO_FOREACH)
 set(CMAKE_CXX_STANDARD 14)
 ########### CMake Config Files ###########