How to open pictures in an external application

When right-click an image, Joplin shows me a menu, from which I choose "Open..." In the past, that would launch Gwenview (I'm on Kubuntu 22.04), but now nothing will happen. I installed the AppImage version via the official install script. Please help!

When you click "open" Joplin just "asks" the OS to open the file with whatever program on the system is the default to handle that type. What is the image type you are trying to open?