This page contains videos and other instructions about how to install the Flathub Store and the capability to have flatpaks installed on several different distros that do not come preinstalled with it.
Ubuntu
The video and instructions work on the main distro backed by Canonical and the official distros, like Kubuntu, Xubuntu, and Ubuntu Studio.
Fedora
Fedora uses Flatpaks in its own repository, but the Flathub repository or store also can be installed easily.