No working kit recognised
-
I've been working with 5.11.3/MSVC 2017 on Windows 10 for some time and decided to update to 5.15.2 earlier today after switching to MSVC 2019.
QtCreator won't let me build anything anymore now.

What have I done wrong and/or where can I start fixing something?

-
This is a screenshot of the Qt Versions page:

That qmake.exe can also be invoked from a command line but QtCreator says it "does not exist or is not executable".
-
This might probably be of interest too:

I do not understand the two warnings as I ticked installing cmake during the installation of 5.15.2, and the cmake executable does indeed start when I invoke it from the command-line. Apart from this, I'm not even using cmake for anything at the moment, so this shouldn't really make a difference, should it? What am I overlooking?
-
This is a screenshot of the Qt Versions page:

That qmake.exe can also be invoked from a command line but QtCreator says it "does not exist or is not executable".