I'll mention that library maintainers/authors can't even _consider_ modules unless they set C++20 as a requirement. Many/most popular libraries will not do that anytime soon. I maintain a moderately-popular library and my requirement is C++11... now, to be fair, I started it back in 2016-2017; but still, I won't even consider requiring C++20 until C++17-and-earlier application code is close to disappearing.