Install rust, cargo in Colab

kernel.py

# run this once, then reload, and then skip this
!apt install rustc
!gdown --id 1PULtTc-2e9z4bswh_SQqL5oy_4JpfV7c
!chmod +x evcxr_jupyter
!./evcxr_jupyter --install

// install dependency
:dep cmd_lib
use cmd_lib::run_cmd as sh;

rust.py

# just to use with python
!apt install rustc
%env USER=korakot

Managed to run evcxr by proxying the IPC connection to TCP, as it expects. It needs both cargo and rustc installed, and they can be installed via apt, which is faster. Below is code which uses nix instead of apt to install most of the stuff: run once, change runtime and restart.

!rm -rf /root/.local/share/jupyter/kernels

# Nix install
!curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix | sh -s -- install linux --init none --no-confirm
!ln -s /root/.nix-profile/bin /opt/bin

# Install evcxr
!nix-env -f '<nixpkgs>' -iA cargo rustc evcxr sccache
!evcxr_jupyter --install

# Configure evcxr
!mkdir -p /root/.config/evcxr
!printf ":timing\n:sccache 1" > /root/.config/evcxr/init.evcxr

# IPC Proxy (https://stackoverflow.com/a/74821762)
!wget -qO- https://gist.github.com/SpencerPark/e2732061ad19c1afa4a33a58cb8f18a9/archive/b6cff2bf09b6832344e576ea1e4731f0fb3df10c.tar.gz | tar xvz --strip-components=1
!python install_ipc_proxy_kernel.py --quiet --kernel=rust --implementation=ipc_proxy_kernel.py > /dev/null

# To avoid confusion between kernel names
!sed -i 's/"display_name": "Rust"/"display_name": "Rust-TCP"/g' /root/.local/share/jupyter/kernels/rust_tcp/kernel.json

Many thanks to @mateusvmv efforts and friends here in this discussion. I put together a bash script that overwrites the current kernel and spins up a new Rust kernel without manual config:

# This script sets up and spins up a Jupyter Notebook environment with a Rust kernel using Nix and IPC Proxy. 
!wget -qO- https://gist.github.com/wiseaidev/2af6bef753d48565d11bcd478728c979/archive/3f6df40db09f3517ade41997b541b81f0976c12e.tar.gz | tar xvz --strip-components=1
!bash setup_evcxr_kernel.sh