All QML C++ applications hang on app startup on Mac 11 Big Sur. Whereas normal Qt Widget (non-QML) applications work fine. Even Qt sample QML applications hang on startup.
Building application on Mac Big Sur Beta 5 with QMAKE_MACOSX_DEPLOYMENT_TARGET = 10.12 or later solves the issue.
But QMAKE_MACOSX_DEPLOYMENT_TARGET does not work if the application built on earlier mac os versions like 10.13.
Qt version: qt 5.12
Big Sur beta 5
The issue is not observed with Qt5.15