libKleo uses no new APIs.

--- libkleo-19.04.0/CMakeLists.txt.old	2019-04-12 00:16:32.000000000 +0000
+++ libkleo-19.04.0/CMakeLists.txt	2019-04-19 06:31:09.576149789 +0000
@@ -3,7 +3,7 @@
 
 project(libkleo VERSION ${PIM_VERSION})
 
-set(KF5_MIN_VERSION "5.56.0")
+set(KF5_MIN_VERSION "5.54.0")
 
 find_package(ECM ${KF5_MIN_VERSION} CONFIG REQUIRED)
 set(CMAKE_MODULE_PATH ${ECM_MODULE_PATH})
@@ -24,7 +24,7 @@
 
 
 set(LIBKLEO_LIB_VERSION ${PIM_VERSION})
-set(QT_REQUIRED_VERSION "5.10.0")
+set(QT_REQUIRED_VERSION "5.9.0")
 set(KDEPIMTEXTEDIT_VERSION "5.11.0")
 
 find_package(Qt5 ${QT_REQUIRED_VERSION} CONFIG REQUIRED Widgets)