No working instructions for install PySide6 under Ubuntu 24.04

Under Ubuntu 24.04 Qt documentation offers no workable suggestion for how to install PySide6.  This is fairly basic for any Ubuntu PySide6 user!

The generic instructions at https://doc.qt.io/qtforpython-6/ simply state:

> You can obtain the latest stable version by running pip install pyside6. 

But this no longer works!  You get: a long error message starting with:

pip install PySide6
error: externally-managed-environment× This environment is externally managed

I believe this actually started at Ubuntu 23.04.  See e.g. https://www.omgubuntu.co.uk/2023/04/pip-install-error-externally-managed-environment-fix

I don't know whether this is an issue in other Linux distros or just Ubuntu, which I believe is about the commonly used Linux distro at least in the Qt arena.

If you wish to encourage/support use of PySide6 under Ubuntu I feel you really need to give users some help/information about this.  It is very disconcerting to find you cannot even install PySide6, let alone use it!

Finally on a related matter: I don't know how it works/who decides, but while Qt6 and PyQt6 are available as packages for Ubuntu 24.04 installable with `apt get`, while there are plenty of packages available for `python3-pyside2.qt...` there isn't anything for PySide6.  I don't suppose you can influence/cause Ubuntu 24+ to supply similar for PySide6?