With detailed step by step instructions on how to make it work...

Using modules in the big three compilers: a small experiment

 From the article:

The goal of my experiment was to see how easy it is to write code that a) uses C++20 modules, b) can be compiled by GCC, Clang and MSVC without using conditional compilation, c) imports something from the standard library, d) exports at least one templated function, e) has a peculiarity that makes the module harder to find (in my case, the module is named b but the file that contains it is named a.cppm).

The experiment sort of succeeded...