It depends on what you define by lightest, are you looking for smaller binaries, smaller memory footprint, smaller CPU usage. It also depends on the system you are shipping to and how. For instance a Qt application on Linux is going to be just a few kbs since you can just use the system libraries, but you will probably want to ship the lib with your application on Windows which means around 40MB or more. In this case if you are developing for Linux then Qt is lighter, but if you are developing for Windows the you should use Tauri (which will have a binary of around 2MB, but much more memory usage due to the webview).