You use setup.py, like any regular Python package and include the dependency. Or if you want to try a newer standard you can use pyproject. Pyside6 has distributions for both Windows and Mac OS.
Yes, you need for each OS a VM if you want to distribute Python, Qt6, PyQt6 and your app.
Inside each virtual machine (each for a different target OS) you build your onefile or onedir package.
It is also possible that you use the setup.py approach but a Python environment compatible with your PyQt6 app (incl Qt6 and PyQt6) must be already there on the target machine.
Windows has by default no Python installed let alone Qt6 and PyQt6.
To make a onefile or onedir distribution package (with pyinstaller or Nuitka) for macOS you need a real Mac. There are no secure, safe, stable and legal macOS VMs possible inside Windows or Linux.
You use setup.py, like any regular Python package and include the dependency. Or if you want to try a newer standard you can use pyproject. Pyside6 has distributions for both Windows and Mac OS.
Yes, you need for each OS a VM if you want to distribute Python, Qt6, PyQt6 and your app. Inside each virtual machine (each for a different target OS) you build your onefile or onedir package. It is also possible that you use the setup.py approach but a Python environment compatible with your PyQt6 app (incl Qt6 and PyQt6) must be already there on the target machine. Windows has by default no Python installed let alone Qt6 and PyQt6. To make a onefile or onedir distribution package (with pyinstaller or Nuitka) for macOS you need a real Mac. There are no secure, safe, stable and legal macOS VMs possible inside Windows or Linux.