Flatpak's goal to make software installation easier on Linux systems. This
approach was also designed for less experienced users. But the way it is
implemented in Leap 15.2 makes it hard to use.


1) It is not installed per default (other distributions install the packages
during the setup process)

2) The user can install the Flatpak system via the package manager, but after
the installation it requires additional configuration. It seems that there are
no Flatpak repos configured per default.

The main source for Flakpak is flathub.org. 

To make at least the install command lines at Flathub working, I had to

>flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo

Suggestion

a) add the Flathub repo per default
or

b) make a seperate flathub.org repo installation package available