Ubuntu 20.04 に Rust をインストールする手順です。公式サイトの通りです。
https://rustup.rs/

Rust インストール

WSL2 内の Linux にインストールする場合は、下記コマンドで行います。

$ curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

info: downloading installer

Welcome to Rust!

This will download and install the official compiler for the Rust
programming language, and its package manager, Cargo.

It will add the cargo, rustc, rustup and other commands to
Cargo's bin directory, located at:

  /home/tkondou/.cargo/bin

This can be modified with the CARGO_HOME environment variable.

Rustup metadata and toolchains will be installed into the Rustup
home directory, located at:

  /home/tkondou/.rustup

This can be modified with the RUSTUP_HOME environment variable.

This path will then be added to your PATH environment variable by
modifying the profile file located at:

  /home/tkondou/.profile

You can uninstall at any time with rustup self uninstall and
these changes will be reverted.

Current installation options:


   default host triple: x86_64-unknown-linux-gnu
     default toolchain: stable
               profile: default
  modify PATH variable: yes

1) Proceed with installation (default)
2) Customize installation
3) Cancel installation
>1

1 でインストールします。

再起動

インストール後、SHELLを再起動します。

$ exec $SHELL -l

確認

cargo、rustc 、rustup コマンドが使えました！

$ cargo --version
cargo 1.54.0 (5ae8d74b3 2021-06-22)

$ rustc --version
rustc 1.54.0 (a178d0322 2021-07-26)

$ rustup --version
rustup 1.24.3 (ce5817a94 2021-05-31)
info: This is the version for the rustup toolchain manager, not the rustc compiler.
info: The currently active `rustc` version is `rustc 1.54.0 (a178d0322 2021-07-26)`

rust の更新 (rustup update)

rustup update コマンドで rust を更新できます。

❯ rustup update
info: syncing channel updates for 'stable-x86_64-unknown-linux-gnu'
info: latest update on 2021-12-02, rust version 1.57.0 (f1edd0429 2021-11-29)
info: downloading component 'cargo'
info: downloading component 'clippy'
info: downloading component 'rust-docs'
info: downloading component 'rust-std'
info: downloading component 'rustc'
info: downloading component 'rustfmt'
info: removing previous version of component 'cargo'
info: removing previous version of component 'clippy'
info: removing previous version of component 'rust-docs'
info: removing previous version of component 'rust-std'
info: removing previous version of component 'rustc'
info: removing previous version of component 'rustfmt'
info: installing component 'cargo'
info: installing component 'clippy'
info: installing component 'rust-docs'
 17.9 MiB /  17.9 MiB (100 %)  15.1 MiB/s in  1s ETA:  0s
info: installing component 'rust-std'
 24.9 MiB /  24.9 MiB (100 %)  19.1 MiB/s in  1s ETA:  0s
info: installing component 'rustc'
 53.9 MiB /  53.9 MiB (100 %)  21.2 MiB/s in  2s ETA:  0s
info: installing component 'rustfmt'
info: checking for self-updates

  stable-x86_64-unknown-linux-gnu updated - rustc 1.57.0 (f1edd0429 2021-11-29) (from rustc 1.56.1 (59eed8a2a 2021-11-01))

info: cleaning up downloads & tmp directories