diff --git a/CMakeLists.txt b/CMakeLists.txt
index 29ea9c7466c..1af0c4c89c8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -431,48 +431,96 @@ if(WITH_CORE)
   endif()
 
   #############################################################
-  # search for Qt5
-  set(QT_MIN_VERSION 6.0.0)
+  # search for Qt
+
+  set (WITH_QT6 TRUE CACHE BOOL "Enable (broken, experimental) Qt6 support")
+  if (WITH_QT6)
+    set(QT_MIN_VERSION 6.0.0)
+  else()
+    set(QT_MIN_VERSION 5.12.0)
+  endif()
 
   # Use Qt5SerialPort optionally for GPS
   set (WITH_QT5SERIALPORT TRUE CACHE BOOL "Determines whether Qt5SerialPort should be tried for GPS positioning")
   if (WITH_QT5SERIALPORT)
-      find_package(Qt6 COMPONENTS SerialPort REQUIRED)
+      if (WITH_QT6)
+	find_package(Qt6 COMPONENTS SerialPort REQUIRED)
+      else()
+	find_package(Qt5 COMPONENTS SerialPort REQUIRED)
+      endif()
       # following variable is used in qgsconfig.h
       set (HAVE_QT5SERIALPORT TRUE)
   endif()
 
-  find_package(Qt6 COMPONENTS Core Gui Widgets Network Xml Svg Concurrent Test UiTools Sql REQUIRED)
+  if (WITH_QT6)
+    find_package(Qt6 COMPONENTS Core Gui Widgets Network Xml Svg Concurrent Test UiTools Sql REQUIRED)
+  else()
+    find_package(Qt5 COMPONENTS Core Gui Widgets Network Xml Svg Concurrent Test UiTools Sql REQUIRED)
+  endif()
   if (NOT IOS)
-    find_package(Qt6 COMPONENTS PrintSupport REQUIRED)
+    if (WITH_QT6)
+      find_package(Qt6 COMPONENTS PrintSupport REQUIRED)
+    else()
+      find_package(Qt5 COMPONENTS PrintSupport REQUIRED)
+    endif()
   else()
     add_definitions(-DQT_NO_PRINTER)
   endif()
-  find_package(Qt6 COMPONENTS Positioning)
-  if (WITH_QTWEBKIT)
+  if (WITH_QT6)
+    find_package(Qt6 COMPONENTS Positioning)
+  else()
+    find_package(Qt5 COMPONENTS Positioning)
+  endif()
+  if (WITH_QTWEBKIT AND NOT WITH_QT6)
     find_package(Qt5WebKit REQUIRED)
     find_package(Qt5WebKitWidgets REQUIRED)
   endif()
   if (WITH_3D)
-    find_package(Qt6 COMPONENTS 3DCore 3DRender 3DInput 3DLogic 3DExtras REQUIRED)
+    if (WITH_QT6)
+      find_package(Qt6 COMPONENTS 3DCore 3DRender 3DInput 3DLogic 3DExtras REQUIRED)
+    else()
+      find_package(Qt5 COMPONENTS 3DCore 3DRender 3DInput 3DLogic 3DExtras REQUIRED)
+    endif()
     set(HAVE_3D TRUE)  # used in qgsconfig.h
   endif()
   if (APPLE)
-    find_package(Qt6 COMPONENTS MacExtras REQUIRED)
+    if (WITH_QT6)
+      find_package(Qt6 COMPONENTS MacExtras REQUIRED)
+    else()
+      find_package(Qt6 COMPONENTS MacExtras REQUIRED)
+    endif()
   endif()
 
   # get the Qt plugins directory
-  get_target_property(QMAKE_EXECUTABLE Qt6::qmake LOCATION)
+  if (WITH_QT6)
+    get_target_property(QMAKE_EXECUTABLE Qt6::qmake LOCATION)
+  else()
+    get_target_property(QMAKE_EXECUTABLE Qt5::qmake LOCATION)
+  endif()
+
   EXEC_PROGRAM(${QMAKE_EXECUTABLE} ARGS "-query QT_INSTALL_PLUGINS" RETURN_VALUE return_code OUTPUT_VARIABLE DEFAULT_QT_PLUGINS_DIR )
   set (QT_PLUGINS_DIR ${DEFAULT_QT_PLUGINS_DIR} CACHE STRING "Path to installation directory for Qt Plugins. Defaults to Qt native plugin directory")
 
-  message(STATUS "Found Qt version: ${Qt6Core_VERSION_STRING}")
+  if (WITH_QT6)
+    message(STATUS "Found Qt version: ${Qt6Core_VERSION_STRING}")
+  else()
+    message(STATUS "Found Qt version: ${Qt5Core_VERSION_STRING}")
+  endif()
   if (WITH_QUICK)
-    find_package(Qt6 COMPONENTS Qml Quick REQUIRED)
-    if(${CMAKE_SYSTEM_NAME} MATCHES "Android")
+    if (WITH_QT6)
+      find_package(Qt6 COMPONENTS Qml Quick REQUIRED)
+      if(${CMAKE_SYSTEM_NAME} MATCHES "Android")
 	find_package(Qt6 COMPONENTS AndroidExtras)
+      else()
+	find_package(QtQmlTools)
+      endif()
     else()
-        find_package(QtQmlTools)
+      find_package(Qt5 COMPONENTS Qml Quick REQUIRED)
+      if(${CMAKE_SYSTEM_NAME} MATCHES "Android")
+	find_package(Qt5 COMPONENTS AndroidExtras)
+      else()
+	find_package(QtQmlTools)
+      endif()
     endif()
 
     # following variable is used in qgsconfig.h
@@ -493,14 +541,18 @@ if(WITH_CORE)
   endif()
 
   # Password helper
-  find_package(QtKeychain REQUIRED)
-  # Master password hash and authentication encryption
-  find_package(QCA REQUIRED)
-  # Check for runtime dependency of qca-ossl plugin
-  # REQUIRED if unit tests are to be run from build directory
-  if(NOT MSVC)
-  include(QCAMacros)
-  FIND_QCAOSSL_PLUGIN_CPP(ENABLE_TESTS)
+  if (WITH_QT6)
+    # nope, not yet!
+  else()
+    find_package(QtKeychain REQUIRED)
+    # Master password hash and authentication encryption
+    find_package(QCA REQUIRED)
+    # Check for runtime dependency of qca-ossl plugin
+    # REQUIRED if unit tests are to be run from build directory
+    if(NOT MSVC)
+      include(QCAMacros)
+      FIND_QCAOSSL_PLUGIN_CPP(ENABLE_TESTS)
+    endif()
   endif()
 
   if (APPLE)