I suspect that your issue is related to the KDE UI and Fiddler Everywhere not setting the proxy settings in the graphical interface. Could you please try the solution suggested in this KB article and let me know if that resolves the issue on your side?
I'm using Kubuntu 20.04 and I'm having issues to run Fiddler. If I just open Fiddler it shows an error when I try to login: "No internet access and it seems you have a proxy set. Check if it is correct in your OS settings and restart the application after that."
But I don't have any setted proxy
If I run the AppImage with sudo it works.
`sudo ./fiddler.AppImage --no-sandbox`
What can I do here to use Fiddler without sudo?