As qt5 moves along it is using new SDK features (as fully expected) and in the process leaving behind lots of systems.
Patching qt5 to use older SDKs is hard as they use non-trivial features. Adding these features to older MacOS versions via the legacysupport PG is also very difficult / nearly impossible as they are generally complex MacOS technologies that aren't backportable. It seems the only long-term solution here would be to somehow enable a qt5-x11 version to build on MacOS (there once was a qt4-x11 version, so it's perhaps not impossible), and then transition systems to that once they reach a certain vintage. Ken
