https://flatpak.org/setup/Ubuntu/ says >4. Restart > >To complete setup, restart your system. Actually a restart may not be necessary, logging out of the desktop and logging in again may be [sufficient](https://github.com/flatpak/flatpak/issues/17#issuecomment-445044576). (Why is this even needed?)