Two different meanings of Rust Minecraft
Horizon is a third-party reimplementation of Minecraft: Java Edition in Rust. A Minecraft mod inspired by the game Rust is a different project. The Horizon repository is the direct source for its launcher and compatibility claims.
Before trying a build
Read the current release notes for platform support and the version it targets. Keep an independent copy of any world you care about and use a fresh world first. Mojang’s launcher remains the source for the original game.