You're reading the documentation for a version of ROS 2 that has reached its EOL (end-of-life), and is no longer officially supported. If you want up-to-date information, please have a look at Galactic.
Building ROS 2 on Fedora Linux
How to setup the development environment?
The following system dependencies are required to build ROS 2 on Fedora. They can be installed with
dnf as follows:
$ sudo dnf install \ asio-devel \ cmake \ cppcheck \ eigen3-devel \ gcc-c++ \ liblsan \ libXaw-devel \ libyaml-devel \ make \ opencv-devel \ patch \ python3-argcomplete \ python3-colcon-common-extensions \ python3-coverage \ python3-devel \ python3-empy \ python3-lark-parser \ python3-lxml \ python3-mock \ python3-mypy \ python3-nose \ python3-pep8 \ python3-pip \ python3-pydocstyle \ python3-pyflakes \ python3-pyparsing \ python3-pytest \ python3-pytest-cov \ python3-pytest-mock \ python3-pytest-runner \ python3-rosdep \ python3-setuptools \ python3-vcstool \ python3-yaml \ poco-devel \ poco-foundation \ python3-flake8 \ python3-flake8-import-order \ redhat-rpm-config \ tinyxml-devel \ tinyxml2-devel \ uncrustify \ wget
With this done, you can follow the rest of the instructions to fetch and build ROS 2.