I would add Windows kernel to that list. Overall seems pretty solid. DirectX 12 too. Visual Studio.

Yeah GitHub/TypeScript kinda don't count. I have an ignorant question though : do people use c# or f# in a non-windows system, by choice ? Otherwise, wouldn't that be a self fulfilling need ?

Edit: typo

Yes, version 5 of the .NET platform (incl C# and F#) runs on Linux and MacOS, and people choose those languages over other languages because of their independent benefits (ie; C# has advantages over Java, and F# has advantages over Haskell/OCaml/etc).

I have not used them myself.

Bit of an aside, but TypeScript was invented at MSFT, and they still maintain it – why would it not count? (Other than not being a consumer product).

And Lean, I think, not that I know how to use it, but it seems to be respected in its world.