Compiling problem on 6.9 with Raspberry Pi 4 (Bookworm)

[ocean71]

I hope you can help me.

I am having problems compiling the latest 6.9 for my Pi4. I installed 6.8 OK.
I downloaded and installed qwt 6.3.0 as per the instructions and installed the required libraries including the Qt6 ones. The FindQwt module file was amended accordingly to reflect correct paths.

Using Cmake, I manage to get 74% of the compiling when it throws up an error.

I would be very grateful for some advice on how to sort the problem out.

This is what happens:

[ 74%] Building CXX object CMakeFiles/Qt-DAB.dir/home/xxxxxx/Downloads/qt-dab-Qt-DAB-6.9/src/output/Qt6/Qt-audio.cpp.o
/home/xxxxxx/Downloads/qt-dab-Qt-DAB-6.9/src/output/Qt6/Qt-audio.cpp: In member function ‘virtual void Qt_Audio::restart()’:
/home/xxxxxx/Downloads/qt-dab-Qt-DAB-6.9/src/output/Qt6/Qt-audio.cpp:110:9: error: ‘QtAudio’ has not been declared
110 | QtAudio::Error err = m_audioSink -> error ();
| ^~~~~~~
/home/xxxxxx/Downloads/qt-dab-Qt-DAB-6.9/src/output/Qt6/Qt-audio.cpp:111:50: error: ‘err’ was not declared in this scope; did you mean ‘erf’?
111 | fprintf (stderr, "Errorcode %d\n", (int)(err));
| ^~~
| erf
make[2]: *** [CMakeFiles/Qt-DAB.dir/build.make:2095: CMakeFiles/Qt-DAB.dir/home/xxxxxx/Downloads/qt-dab-Qt-DAB-6.9/src/output/Qt6/Qt-audio.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:102: CMakeFiles/Qt-DAB.dir/all] Error 2
make: *** [Makefile:136: all] Error 2

I hope someone can solve this for me. Many thanks for your help.