Install pnpm if you don't have it installed:
npm i -g pnpm@6
Install lsp-ws-proxy (v0.4.0+) by downloading a binary from releases and moving it in PATH.
Install rust-analyzer by downloading a binary from releases and moving it in PATH.
You can also save the binary to ./bin/rust-analyzer because ./bin is prepended to PATH when starting the proxy.
Make sure to make the binaries executables with chmod +x rust-analyzer if it's not already set.
In project root:
pnpm install
In this directory:
pnpm dev