In 6.10.0, compiling with cmake with

  cmake -B build -S pyside-setup -G Ninja \
    -DCMAKE_INSTALL_PREFIX=/usr \
    -DCMAKE_BUILD_TYPE=None \
    -DSHIBOKEN_PYTHON_LIBRARIES=`pkgconf python3-embed --libs` \
    -DBUILD_TESTS=OFF \
    -DFORCE_LIMITED_API=no \
    -DNO_QT_TOOLS=yes
  cmake --build build

Installs headers to the non-standard (hardcoded!) paths /usr/PySide6/include. This violates the Linux File Hierarchy Standard, which mandates headers to be installed under /usr/incude, and creates directories which are completely alien to a standard Linux system. At the very least, this should be configurable.