- KDE neon user mixes KF5 and KF6 and I can't get the dependencies to install
- KDE neon unstable was not actually used
- Fedora seems more stable for CI purposes.

All other CI jobs use pybind11.

Fedora Linux 40 has the necessary components as part of upgrading
to KDE Plasma 6.

Needs "qt5" for the Qt5 version, and no suffix for Qt6. Now we can
at least spot the build error in neon-nightly.

SEE #2202

Let this run overnight so we can see the appstream-api-change locally.

See #2202