Your software manager is your Linux app store. Allow your browser to open it, then choose Install.
Open in software managerПеред установкой обязательно прочтите руководство по установке для вашего дистрибутива Linux
Open the file from your downloads folder in your software manager, then choose Install.
The .flatpakref file points to the app. Downloading it does not install it.
After setup, paste this into a terminal on your Linux computer and press Enter.
flatpak install flathub org.gnome.SimpleScan