Ristretto is a free and open source image viewer for Linux. It comes with Linux Xfce desktop environment but you can also install on any other desktop environments like Gnome and KDE. Using Ristretto you can view images and play images as image slideshow, edit image with external image editor and set the image as your desktop wallpaper. It is fast and lightweight image viewer.
Install Ristretto Image Viewer on Ubuntu Linux
Ristretto is available as flatpak package from flathub remote repository. Follow below link for flatpak and flathub installation instructions. After that restart your system.
Now open the command-line terminal application (ctrl+alt+t) and run below Ristretto flatpak install command. It will install the latest version of Ristretto on your system.
flatpak install flathub org.xfce.ristretto
Now run below command to start Ristretto. You can also run it from the applications menu.
flatpak run org.xfce.ristretto
And you can also uninstall it via this command.
sudo flatpak uninstall org.xfce.ristretto