Python cryptography, Rust, and Gentoo

> It adds backward compatibility breaks.

Rust cares quite a bit about *not* having backwards compatibility issues. A project dropping compatibility with ancient platforms would be a potential backwards compatibility break in that project, not in Rust.

> Rust is being promoted as a systems language when it doesn’t work on all of the hardware needed by a systems language.

Only if you're tautologically defining "all the hardware needed by a systems language" as "every platform that has ever had a C compiler".

Rust runs on most current platforms, and many non-current ones.