To install Flatpak on Ubuntu 18.10 (Cosmic Cuttlefish) or later, open the Terminal app and run:
Flathub is the best place to get Flatpak apps. To enable it, download and install the Flathub repository file or run:
With Flathub enabled, install Bazaar directly from Flathub by running:
Then launch it from your desktop to install Flatpak apps graphically.
To complete setup, restart your system. Now all you have to do is install apps!