If you need memory safety, precise control over low-level runtime behavior (e.g., no tracing garbage collector), concurrency, and a strong ecosystem, Rust is pretty much your only option.
The alternative that comes closest to being viable, in my view, is Swift. Swift currently offers memory safety or concurrency, but not both at once. They're working on fixing this, but they haven't yet. Additionally, hopes that it would grow a strong ecosystem for non-Apple platforms (like Linux servers) don't seem to have panned out, largely because Apple owns the language and they don't seem to care very much about this use case.
As for the other low-level languages I'm aware of that aren't C or C++ or assembly and aren't hopelessly obscure:
Ada seems to be interested in adopting Rust-style memory safety, but (as far as I understand) it hasn't yet. It's also not a widely-used language with a strong ecosystem, at least outside of some narrow application domains that probably aren't what you have in mind.
D offers memory safety or precise control over low-level runtime behavior, but not (as far as I understand) both at once. It also doesn't have a strong ecosystem.
Jai doesn't have a publicly available implementation.
Nim offers precise control over low-level runtime behavior or concurrency, but not both at once (because threads can't share memory; there seem to be ways around this with globals but I'm not sure if they let you do everything you can do in C/C++/Rust/Swift). Also, precise control over low-level runtime behavior isn't the default; you have to opt in. And it's not a widely-used language with a strong ecosystem.
Objective-C isn't memory safe, has no plans to fix this, and its ecosystem is likely to decline with time as Apple pushes people to abandon it in favor of Swift.
Verona is a research project without a working implementation yet.
Zig isn't memory safe and has no plans to fix this. It also doesn't have a strong ecosystem. (I don't know anything about its concurrency support.)
If you don't need precise control over your program's low-level runtime behavior, then there are many options available to you. (Go, despite sometimes being marketed as a "systems" language, is in this category; I would also classify Julia, Kotlin/Native, and V here.) More details about your requirements would be needed in order to choose among them.