It's not C++20, but there's plenty of modern C++ (17, 14 mostly; the project started in 2015-ish): https://github.com/arbor-sim/arbor https://github.com/arbor-s

It's not C++20, but there's plenty of modern C++ (17, 14 mostly; the project started in 2015-ish): https://github.com/arbor-sim/arbor https://github.com/arbor-sim/arbor