State of Qt5 in distributions

[Ilya K]

As far as nixpkgs goes, we're still shipping Qt5, but we have dropped qt5-webengine (thanks Emily and Grimmauld for this!) as the biggest attack surface, and we're only shipping enough KF5 to build the Plasma 6 integration bits and Maui, and no new package is allowed to depend on it. Most KDE applications that don't have Qt6 versions have either been dropped or moved to build from pre-releases.