Rapier is an open source physics framework written in Rust.
This project pits godots built-in physics against Rapier. It uses godot-rust to integrate rustcode in godot using gdnative.
note: Godots built-in physics has an open issue for the instability when stacking a lot of rigid bodies: godotengine/godot#2092
finally the webgl export of godot games using gdnative rust works (see the whole conversation)