- Rust is at this moment more mature and stable than Zig or Nim with a more broad ecosystem. I don't know much about Ada but I think there are some technical issues there.

Rust's security guarantees can hold in Rust code that's written for the kernel though. I'm not sure where you got the idea that they can't hold.

Nim has a GC, so that's completely out from being used in the kernel and Zig doesn't offer any security benefits that aren't just slow runtime checks.

I'm not sure what you're referring to?

Zig isn't improving correctness too much either. It provides some niceties, but no guarantees around correctness if I understand correctly. It's not trivial - here's a whole post about it https://www.scattered-thoughts.net/writing/how-safe-is-zig/