aqtinstall: qt.qpa.plugin: Could not find the Qt platform plugin "cocoa" in ""

I installed Qt 5.12.7 with aqt install 5.12.7 mac desktop and installed Qt Creator via Homebrew (brew cask install qt-creator).

I configured Qt Creator kits to use the one install via aqt and I can compile a simple widget project.

Unfortunately, I have the following error when starting it in debug mode:

QFactoryLoader::QFactoryLoader() checking directory path "/Users/martin/dev/build/pouet/Qt_5_12_7_clang_64_from_aqt/Debug/pouet.app/Contents/MacOS/platforms" ...
qt.qpa.plugin: Could not find the Qt platform plugin "cocoa" in ""
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

The program has unexpectedly finished.

QT_DEBUG_PLUGINS is set to 1 as adviced here: https://forum.qt.io/topic/98816/qt-could-not-find-the-platform-plugin-cocoa/8

Any idea what’s going on?