Ubuntu 22.04 (Jammy) ships Python 3.10 as the default. Python 3.11 is not in the main Ubuntu 22.04 repository. Use the deadsnakes PPA. Note that `python3.11-venv` must be installed separately from `python3.11`. Ubuntu's `python3` symlink points to 3.10 — use `python3.11` explicitly or set up pyenv.