QT version (or so it seems)

Hello

Reading the read-me, at `uv run --extra cpu demo_toolbox.py` i get this error:

  × Failed to build `pyqt5==5.15.6`
  ├─▶ The build backend returned an error
  ╰─▶ Call to `sipbuild.api.build_wheel` failed (exit status: 1)

it seems the recent version of QT (6) is not supported? Any pointers that will avoid having 2 versions of QT installed welcome.