Qt application gets stuck trying to open main window under Big Sur

(Not sure of the component, but it's a best guess)

Forum thread: https://forum.qt.io/topic/119316/mac-application-built-with-5-12-9-lts-hangs-on-launch-under-big-sur

Sample data from Activity Monitor: https://gist.githubusercontent.com/NattyNarwhal/57c063578046b1ce6af3cff8b648b357/raw/cc50436506e0e455810465a8d10c17635086cefc/gistfile1.txt

I have an application built under the latest Qt LTS on my system with High Sierra. People running the application on Big Sur report it hangs wasting CPU at 100% and doesn't display the window; testing on HS, Mojave, and Catalina seems to say it's fine.

To repeat the facts from the forum thread:

• The application launches to creating and attaching its menu bar (which is part of the top-level window), but hangs there
• The only "weird" library in use is Qt5DBus (which isn't important to the functioning of the application), everything else is just Widgets without any network/WebKit/GL/etc
• The application gets the system daemon tccd angry with it, and calms down when you force quit the app. I've tried using Taccy to observe it, and I can't really make sense of the logs yet.
• The application is unsigned; I'm not going to bother signing this app if it won't work on Big Sur �