I have encountered an issue on Windows with MSVC and -Dintrospection=enabled.
The build fails on:
src\meson.build:100:2: ERROR: <ExternalProgram 'python3' -> ['C:\\hostedtoolcache\\windows\\Python\\3.12.3\\x64\\python.exe']> is not a valid python or it is missing setuptools

It also have been reported at the gvsbuild, a package to help building GTK on Windows.

I managed to resolve it locally but when trying to verify the fix on Github Actions, the build fails.