nyx-serve is a library for the Nyx language, so the only thing to install is the Nyx toolchain itself — the compiler, the package manager and the standard library, in one directory under your home.
$ curl -sSf https://nyxlang.com/install.sh | sh
The installer puts everything in ~/.nyx and links the
nyx command into ~/.local/bin. If that
directory is not on your PATH, the installer tells you
the exact line to add to your shell profile.
$ nyx --version nyx 0.22.0
Nyx compiles through LLVM, so you also need clang —
most Linux distributions and macOS already have it. Check with
clang --version; on Debian/Ubuntu it is
apt install clang.