The Outline app allows users with access keys to connect to the Outline server and the open web through their connected devices.
Connect to your server using your unique access key, generated by the Outline Manager. Since it’s primary function is to encrypt your device’s internet traffic, you must have an access key from an Outline server administrator in order to use it effectively. This access key contains an encryption code or password that allows your device to communicate with the Outline server.
Flatpak version doesn't work. Probably missed "sudo needed" with combination of Flatpak default permissions.