diff -Nur qwt-6.1.5.old/qwtbuild.pri qwt-6.1.5/qwtbuild.pri
--- qwt-6.1.5.old/qwtbuild.pri	2020-06-01 20:48:07.321112118 +0400
+++ qwt-6.1.5/qwtbuild.pri	2020-09-19 01:05:19.842096481 +0400
@@ -14,7 +14,7 @@
 CONFIG           += qt
 CONFIG           += warn_on
 CONFIG           += no_keywords
-CONFIG           += silent
+#CONFIG           += silent
 
 DEFINES += QT_NO_DEPRECATED_WARNINGS # not fixing those before Qwt 6.2
 
diff -Nur qwt-6.1.5.old/qwtconfig.pri qwt-6.1.5/qwtconfig.pri
--- qwt-6.1.5.old/qwtconfig.pri	2020-06-01 20:48:07.325112226 +0400
+++ qwt-6.1.5/qwtconfig.pri	2020-09-19 01:10:47.546615714 +0400
@@ -19,7 +19,7 @@
 QWT_INSTALL_PREFIX = $$[QT_INSTALL_PREFIX]
 
 unix {
-    QWT_INSTALL_PREFIX    = /usr/local/qwt-$$QWT_VERSION
+    # QWT_INSTALL_PREFIX    = /usr/local/qwt-$$QWT_VERSION
     # QWT_INSTALL_PREFIX = /usr/local/qwt-$$QWT_VERSION-qt-$$QT_VERSION
 }
 
@@ -29,8 +29,8 @@
 }
 
 QWT_INSTALL_DOCS      = $${QWT_INSTALL_PREFIX}/doc
-QWT_INSTALL_HEADERS   = $${QWT_INSTALL_PREFIX}/include
-QWT_INSTALL_LIBS      = $${QWT_INSTALL_PREFIX}/lib
+QWT_INSTALL_HEADERS   = $$[QT_INSTALL_HEADERS]/qwt
+QWT_INSTALL_LIBS      = $$[QT_INSTALL_LIBS]
 
 ######################################################################
 # Designer plugin
@@ -42,7 +42,8 @@
 # runtime environment of designer/creator.
 ######################################################################
 
-QWT_INSTALL_PLUGINS   = $${QWT_INSTALL_PREFIX}/plugins/designer
+#QWT_INSTALL_PLUGINS   = $${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
@@ -110,7 +111,7 @@
 # to your qmake project file.
 ######################################################################
 
-#QWT_CONFIG     += QwtMathML
+QWT_CONFIG     += QwtMathML
 
 ######################################################################
 # If you want to build the Qwt designer plugin,