Tools are getting to 20.

Standard C++20 Modules support with MSVC in Visual Studio 2019 version 16.8

by Cameron DaCamara

From the article:

It has been some time since our last update regarding C++ Modules conformance. The toolset, project system, and IDE teams have been hard at work to create a first class C++ Modules experience in Visual Studio 2019. There is a lot to share, so let’s get right into it...