How much of C++20 standard Circle already supports?

[Shadoware]

Sorry but I didn't find the information of what is currently supported.

I would like to know in what C++ compiler was Circle based? Maybe Clang?

Make simple information like these more obvious.

P.S. I've discussing about Circle in some C++ forums like Reddit and others and it seems the mains complaint is that Circle is not Open Source so people feels unsafe for it's future.