Replaced in the QZXIng cmake file Qt5 -> Qt6 and set if(QZXING_MULTIMEDIA)
LIST(APPEND SOURCES QZXingFilterVideoSink.cpp QZXingFilterVideoSink.h)
add_definitions(-DQZXING_MULTIMEDIA)
SET(QZXING_USE_QML ON)
endif(QZXING_MULTIMEDIA)
instead of QZXingFilter.[cpp,h]