Whenever I see "... in Rust" because it is such a popular for hobby projects that are prone to being abandoned. Of course, that might happen to any project in any language, but something tells me that if you manage to get a C codebase to a functional and maintainable point, there is already some energy behind the initiative. There are counter-examples (first and foremost Ripgrep), but I have become so prejudiced in this matter that I'm always skeptical until proven otherwise.

People often do projects like this to learn a new language. Nothing wrong with that. Rust is being used in production quite a bit these days.

How do you determine that a project is dead? (In general)

Here, I see activity 3 months ago in June. The README doesn't say anything.

The insight contributors chart is usually a good clue. It’s not perfect because it only shows the main branch configured in GitHub and some project haven’t merged to main in years.

Still, it’s good to see how many big contributors a project has, and how active they are over time.

https://github.com/feather-rs/feather/graphs/contributors

The last commit before that was in Februrary 2022.