Where is the ROS distributions folder in Debian?

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Hello, I'm new in ROS, I'm trying to use the qtcreator plugin but I no know where is the ROS distibutions folder, I just installed ROS from the official doc for Debian. An interesting details is that looking at the Packages content:

wget -qO- http://packages.ros.org/ros/ubuntu/dists/buster/main/binary-amd64/Packages | grep Package

I have the following output:

Package: python-bloom
Package: python-catkin-pkg
Package: python-catkin-pkg-modules
Package: python-catkin-tools
Package: python-osrf-pycommon
Package: python-rosdep
Package: python-rosdistro
Package: python-rosdistro-modules
Package: python-rosinstall
Package: python-rosinstall-generator
Package: python-rospkg
Package: python-rospkg-modules
Package: python-vcstool
Package: python-vcstools
Package: python-wstool
Package: python3-bloom
Package: python3-catkin-pkg
Package: python3-catkin-pkg-modules
Package: python3-catkin-tools
Package: python3-colcon-argcomplete
Package: python3-colcon-bash
Package: python3-colcon-bazel
Package: python3-colcon-cmake
Package: python3-colcon-common-extensions
Package: python3-colcon-core
Package: python3-colcon-defaults
Package: python3-colcon-devtools
Package: python3-colcon-library-path
Package: python3-colcon-metadata
Package: python3-colcon-mixin
Package: python3-colcon-notification
Package: python3-colcon-output
Package: python3-colcon-package-information
Package: python3-colcon-package-selection
Package: python3-colcon-parallel-executor
Package: python3-colcon-pkg-config
Package: python3-colcon-powershell
Package: python3-colcon-python-setup-py
Package: python3-colcon-recursive-crawl
Package: python3-colcon-ros
Package: python3-colcon-test-result
Package: python3-colcon-zsh
Package: python3-osrf-pycommon
Package: python3-px4sitl
Package: python3-rocker
Package: python3-rosdep
Package: python3-rosdistro
Package: python3-rosdistro-modules
Package: python3-rosinstall
Package: python3-rosinstall-generator
Package: python3-rospkg
Package: python3-rospkg-modules
Package: python3-vcstool
Package: python3-vcstools
Package: python3-wstool

Maybe this means that most ROS packages was installed from the main Debian repository, I'm trying to use dpkg -L to figure out the relevant folder but I can't, any hint please. There is any link to install melodic from source or with a standalone installer? Than you in advance.