I found the solution, which is easy. Deleting the User/System variable QT_QPA_PLATFORM_PLUGIN_PATH c:\Users\Tomas\AppData\Roaming\Python\Python36\site-packages\PyQt6\Qt6\plugins\platforms solved the problem. This value may be a residual from a previous installation that was not removed. Unfortunately, the new installator is sensitive to this item.
If the Pycharm console or debugger are showing "Could not find or load the Qt platform plugin windows", the Python EXE file may be located at a different location for the PyCharm interpreter.
How to fix "could not find or load the Qt platform plugin windows" while using Matplotlib in PyCharm - Stack Overflow
I am stuck trying to run a very simple Python script, getting this error: qt.qpa.plugin: Could not find the Qt platform plugin "cocoa" in "" This application failed to start bec...
Platforms is the folder directly copied from Qt\Qt5.1.1\5.1.1\msvc2012\plugins\platforms including e.g. qwindows.dll. Does not matter if I rename it to "platform" as some other users did. Qt is still not finding the "platform plugin windows", where is my mistake?
[SOLVED] Qt - This application failed to start because it could not find or load the qt platform plugin windows General and Desktop 18 Posts 4 Posters 24.5k Views 1 Watching
[SOLVED] Qt - This application failed to start because it could not find or load the qt platform plugin windows | Qt Forum
Could not load the Qt platform plugin "windows" even though it was found Unsolved Qt for Python 11 Posts 5 Posters 3.0k Views Oldest to Newest
Could not load the Qt platform plugin "windows" even though it was found
qt.qpa.plugin: Could not find the Qt platform plugin "windows" in "" This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem. I uninstalled python, installed older versions etc. nothing worked.