diff --git a/designer/designer.pro b/designer/designer.pro
index fa4d8c7fd..ce3f82081 100644
--- a/designer/designer.pro
+++ b/designer/designer.pro
@@ -23,8 +23,8 @@ CONFIG( debug_and_release ) {
 
     message("debug_and_release: building the Qwt designer plugin in release mode only")
 
-    CONFIG -= debug_and_release
-    CONFIG += release
+    # CONFIG -= debug_and_release
+    # CONFIG += release
 }
 
 contains(QWT_CONFIG, QwtDesigner ) {
diff --git a/qwtbuild.pri b/qwtbuild.pri
index 9306b6ed0..5b51218b6 100644
--- a/qwtbuild.pri
+++ b/qwtbuild.pri
@@ -54,12 +54,12 @@ win32 {
     # might need a debug version.
     # Enable debug_and_release + build_all if you want to build both.
 
-    CONFIG           += debug_and_release
-    CONFIG           += build_all
+    # CONFIG           += debug_and_release
+    # CONFIG           += build_all
 }
 else {
 
-    CONFIG           += release
+    # CONFIG           += release
 
     VER_MAJ           = $${QWT_VER_MAJ}
     VER_MIN           = $${QWT_VER_MIN}
diff --git a/qwtconfig.pri b/qwtconfig.pri
index 7da1485a0..b69b5ca71 100644
--- a/qwtconfig.pri
+++ b/qwtconfig.pri
@@ -19,18 +19,19 @@ QWT_VERSION      = $${QWT_VER_MAJ}.$${QWT_VER_MIN}.$${QWT_VER_PAT}
 QWT_INSTALL_PREFIX = $$[QT_INSTALL_PREFIX]
 
 unix {
-    QWT_INSTALL_PREFIX    = /usr/local/qwt-$$QWT_VERSION-dev
+    # QWT_INSTALL_PREFIX    = /usr/local/qwt-$$QWT_VERSION-dev
     # QWT_INSTALL_PREFIX = /usr/local/qwt-$$QWT_VERSION-dev-qt-$$QT_VERSION
 }
 
 win32 {
-    QWT_INSTALL_PREFIX    = C:/Qwt-$$QWT_VERSION-dev
+    # QWT_INSTALL_PREFIX    = C:/Qwt-$$QWT_VERSION-dev
     # QWT_INSTALL_PREFIX = C:/Qwt-$$QWT_VERSION-dev-qt-$$QT_VERSION
 }
 
-QWT_INSTALL_DOCS      = $${QWT_INSTALL_PREFIX}/doc
+QWT_INSTALL_DOCS      = $$[QT_INSTALL_DOCS]/doc
-QWT_INSTALL_HEADERS   = $${QWT_INSTALL_PREFIX}/include
+QWT_INSTALL_HEADERS   = $${QWT_INSTALL_PREFIX}/include/qwt
-QWT_INSTALL_LIBS      = $${QWT_INSTALL_PREFIX}/lib
+QWT_INSTALL_LIBS      = $$[QT_INSTALL_LIBS]
+QWT_INSTALL_BINS      = $$[QT_INSTALL_BINS]
 
 ######################################################################
 # Designer plugin
@@ -42,7 +43,7 @@ QWT_INSTALL_LIBS      = $${QWT_INSTALL_PREFIX}/lib
 # runtime environment of designer/creator.
 ######################################################################
 
-QWT_INSTALL_PLUGINS   = $${QWT_INSTALL_PREFIX}/plugins/designer
+QWT_INSTALL_PLUGINS   = $$[QT_INSTALL_PLUGINS]/designer
 
 # linux distributors often organize the Qt installation
 # their way and QT_INSTALL_PREFIX doesn't offer a good
@@ -63,7 +64,7 @@ QWT_INSTALL_PLUGINS   = $${QWT_INSTALL_PREFIX}/plugins/designer
 # with every Qt upgrade.
 ######################################################################
 
-QWT_INSTALL_FEATURES  = $${QWT_INSTALL_PREFIX}/features
+QWT_INSTALL_FEATURES  = $$[QT_INSTALL_DATA]/mkspecs/features
 # QWT_INSTALL_FEATURES  = $$[QT_INSTALL_PREFIX]/features
 
 ######################################################################
@@ -72,7 +73,7 @@ QWT_INSTALL_FEATURES  = $${QWT_INSTALL_PREFIX}/features
 # it will be a static library.
 ######################################################################
 
-QWT_CONFIG           += QwtDll
+# QWT_CONFIG           += QwtDll
 
 ######################################################################
 # QwtPlot enables all classes, that are needed to use the QwtPlot
@@ -114,7 +115,7 @@ QWT_CONFIG     += QwtOpenGL
 # Otherwise you have to build it from the designer directory.
 ######################################################################
 
-QWT_CONFIG     += QwtDesigner
+# QWT_CONFIG     += QwtDesigner
 
 ######################################################################
 # Compile all Qwt classes into the designer plugin instead
@@ -137,7 +138,7 @@ win32 {
 # Otherwise you have to build them from the examples directory.
 ######################################################################
 
-QWT_CONFIG     += QwtExamples
+# QWT_CONFIG     += QwtExamples
 
 ######################################################################
 # The playground is primarily intended for the Qwt development
@@ -148,14 +149,14 @@ QWT_CONFIG     += QwtExamples
 # Otherwise you have to build them from the playground directory.
 ######################################################################
 
-QWT_CONFIG     += QwtPlayground
+# QWT_CONFIG     += QwtPlayground
 
 ######################################################################
 # If you want to auto build the tests, enable the line below
 # Otherwise you have to build them from the tests directory.
 ######################################################################
 
-QWT_CONFIG     += QwtTests
+# QWT_CONFIG     += QwtTests
 
 ######################################################################
 # When Qt has been built as framework qmake wants
@@ -171,8 +172,4 @@ macx:!static:CONFIG(qt_framework, qt_framework|qt_no_framework) {
 # Create and install pc files for pkg-config
 # See http://www.freedesktop.org/wiki/Software/pkg-config/
 ######################################################################
-
-unix {
-
-    QWT_CONFIG     += QwtPkgConfig
-}
+# QWT_CONFIG     += QwtPkgConfig # Qt6 has no pkgconfig files
diff --git a/src/src.pro b/src/src.pro
index 762e4c49b..d70a1b62b 100644
--- a/src/src.pro
+++ b/src/src.pro
@@ -49,27 +50,27 @@ contains(QWT_CONFIG, QwtFramework) {
 include ( $${PWD}/src.pri )
 
 # Install directives
 
 target.path    = $${QWT_INSTALL_LIBS}
 INSTALLS       = target 
 
 CONFIG(lib_bundle) {
 
     FRAMEWORK_HEADERS.version = Versions
     FRAMEWORK_HEADERS.files = $${HEADERS}
     FRAMEWORK_HEADERS.path = Headers
     QMAKE_BUNDLE_DATA += FRAMEWORK_HEADERS
 }
 else {
 
     headers.files  = $${HEADERS}
     headers.path   = $${QWT_INSTALL_HEADERS}
     INSTALLS += headers
 }
 
 contains(QWT_CONFIG, QwtPkgConfig) {
 
-    CONFIG     += create_pc create_prl no_install_prl
+    CONFIG     += create_pc create_prl
 
     QMAKE_PKGCONFIG_NAME = Qwt$${QWT_VER_MAJ}
     QMAKE_PKGCONFIG_DESCRIPTION = Qt Widgets for Technical Applications
@@ -82,14 +81,14 @@ contains(QWT_CONFIG, QwtPkgConfig) {
     greaterThan(QT_MAJOR_VERSION, 4) {
 
         QMAKE_PKGCONFIG_FILE = Qt$${QT_MAJOR_VERSION}$${QMAKE_PKGCONFIG_NAME}
-        QMAKE_PKGCONFIG_REQUIRES = Qt5Widgets Qt5Concurrent Qt5PrintSupport
+        QMAKE_PKGCONFIG_REQUIRES = Qt$${QT_MAJOR_VERSION}Widgets Qt$${QT_MAJOR_VERSION}Concurrent Qt$${QT_MAJOR_VERSION}PrintSupport
 
         contains(QWT_CONFIG, QwtSvg) {
-            QMAKE_PKGCONFIG_REQUIRES += Qt5Svg
+            QMAKE_PKGCONFIG_REQUIRES += Qt$${QT_MAJOR_VERSION}Svg
         }
 
         contains(QWT_CONFIG, QwtOpenGL) {
-            QMAKE_PKGCONFIG_REQUIRES += Qt5OpenGL
+            QMAKE_PKGCONFIG_REQUIRES += Qt$${QT_MAJOR_VERSION}OpenGL
         }
 
         QMAKE_DISTCLEAN += $${DESTDIR}/$${QMAKE_PKGCONFIG_DESTDIR}/$${QMAKE_PKGCONFIG_FILE}.pc