My favorite part about Niri is that a bunch of people said that writing a Wayland compositor in Rust was too hard to do for years. Turns out they're wrong!
The majority of the projects in this comment chain don't actually independently implement a compositor in Rust - which is a good thing IMHO. Cosmic and Pinaccle at least come from a common core written in rust that is associated with the cosmic project: https://github.com/Smithay/smithay/
I haven't checked the repo but just carefully use unsafe as an escape hatch when needed and Rust gets out of your way. Sure you give away some of the guarantees that some people get cultish about but you get to tap into a beautiful ecosystem and reap the benefits.
Playing with client-side Wayland programming, wayrs is a lot nicer to deal with than the C library wrappers.
https://github.com/MaxVerevkin/wayrs