I've successfully built apps with Python and Qt (PyQt6 and PySide6 are both working fine). The overall file size of the resulting folder is about 60-80 MB on Windows, mostly due to all the Qt DLLs/plugins you'll need to ship. By manually deleting non-necessary DLLs, you might save maybe up to 20 MB. Just considering the file size, this might not a huge gain compared to Electron, I suppose?
However, keep in mind that desktop apps have the major disadvantage of figuring out distribution (separately for each platform!!), which includes the following two steps: 1) packaging the application in some format (e.g. an MSI installer for Windows and a Disk Image Bundle for macOS), and 2) distributing that package (including auto-updates). I have written a number of articles about this topic, see https://www.augmentedmind.de/2021/05/30/distributing-windows... and https://www.augmentedmind.de/2021/06/13/distributing-macos-a... . You get rid of all that if you just built a PWA or other kind of web app.
However, keep in mind that desktop apps have the major disadvantage of figuring out distribution (separately for each platform!!), which includes the following two steps: 1) packaging the application in some format (e.g. an MSI installer for Windows and a Disk Image Bundle for macOS), and 2) distributing that package (including auto-updates). I have written a number of articles about this topic, see https://www.augmentedmind.de/2021/05/30/distributing-windows... and https://www.augmentedmind.de/2021/06/13/distributing-macos-a... . You get rid of all that if you just built a PWA or other kind of web app.
In addition, if you use Python, you also need to choose a "freezing" solution, such as PyInstaller (more details at https://www.augmentedmind.de/2021/05/16/distribute-python-ap... ).