The std::future::Future from the rust standard library works with every runtime.
Not sure I understand, what kind of interoperability you are talking about. What kinds of code works in C++ across runtimes, for which the equivalent in Rust doesn't?
In C++ you don't have the scenario like in Rust, where one is forced to use a specific async runtime for library xyz, because it depends on having tokio as runtime.
In Rust you only are forced to use a specific runtime if you want to use its API. For example to spawn new tasks, or to block on a future. I believe that would be the same in C++.
In Rust, you don't need to use a specific runtime if you just want to use async function in your library.
