When initially configuring user projects with a debug configuration, Qt Creator runs CMake with "-DCMAKE_CXX_FLAGS_INIT=-DQT_QML_DEBUG", to enable the QML debugging feature for the build.

Unfortunately that doesn't have any effect, because the toolchain file overwrites that:

/opt/toolchain/sysroots/aarch64-pokysdk-linux/usr/share/cmake/Qt6Toolchain.cmake(31):  set(CMAKE_CXX_FLAGS_INIT  -m64 -march=x86-64-v3 -fstack-protector-strong   -Wformat -Wformat-security -Werror=format-security --sysroot=/opt/toolchain/sysroots/x86-64-v3-poky-linux )

The result is that after users configure their project, QML debugging is disabled. They have to manually re-enable QML debugging in the UI and trigger another CMake run. See the linked bug report QTCREATORBUG-32434