Qt5 end-of-life

[ajtribick]

Qt 5.15 has reached end-of-life and the Qt documentation website has removed the switch to toggle to Qt 5.15 documentation (although it seems that for now it can be accessed by manually modifying the ULRs). It may be worth considering if we want to continue to support the Qt5 build, or to simplify to be Qt6-only.

[munix9]

If possible, Qt5 support should be made available for a while longer, perhaps until the end of 2025.
LTS versions of certain distributions in particular still have no or only insufficient qt6 support.

The packages for Debian 11, for example, are currently built without Qt6.
Of course, this also depends on the effort that would be necessary for further Qt5 support.

[375gnu]

Debian 11 EOL is scheduled to August 31st, 2026. Let's keep Qt until that day.