Flatpak in Ubuntu 18.04 (not in 20.04)

Install Flatpak

The official Flatpak PPA is the recommended way to install Flatpak. To install it, run the following in a terminal:

sudo add-apt-repository ppa:alexlarsson/flatpak

sudo apt update

sudo apt install flatpak

Install the Software Flatpak plugin

The Flatpak plugin for the Software app makes it possible to install apps without needing the command line. To install, run:

sudo apt install gnome-software-plugin-flatpak

Add the Flathub repository

Flathub is the best place to get Flatpak apps. To enable it, run:

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

Restart

To complete setup, restart your system. Now all you have to do is install some apps!

To be able to see tray icons you need to install

sudo apt install gnome-shell-extension-top-icons-plus

Permissions.

There is one issue with permissions in Flatpak apps. Sometimes you need other permissions for your apps to work the way you like them to work.

If you install the app Flatseal, you get an easy tool to change all sorts of permissions.

It is a flatpak app and can be installed using this link