Should Python packaging aim for meson as build system (in case of extension modules)?

Right, I tested only the Nix builds and forgot we use python setup.py bdist in case of setuptools. Changed the instruction.

I assume this is on Windows. I cannot reproduce it otherwise.

The Meson instructions not much else aside from using the build tools prompt as you did.
https://mesonbuild.com/Using-with-Visual-Studio.html#using-with-visual-studio

I have no recent experience of using Python on Windows so can’t look into this any further. It’s a pity though it did not work out of the box.