Thank you very much, did not find this in Github in my first search. And thought this might not be realy a zig issue, so I wanted to ask first in the community.
Currently if you want to use C++ modules, you pretty much have to use CMake with a subset of buildsystems (e.g. it will never work with Make). Currently only ninja (single and multi-config, version 1.11+) and VS Studio 17 2022 (and up) are supported. And even then Header units aren’t supported (e.g. import "myheader.h";). And all of that while keeping in mind that CMake is pretty much spearheading the implementation together with the compiler implementors.
It will take a LONG time until C++ modules are properly supported everywhere (if at all) since it requires the buildsystem and compiler to work in tandem.