I don't think there's any way of doing it through the desktop environment, but I do think it can be fixed with some tinkering in the terminal
-whatever app controls the desktop effects, is blurring what is behind applications with transparency.
-the pointer must be running as window that is fully transparent apart from the pointer itself. and since it becomes the active window, the presentation is considered to be behind the active window so it gets blurred.
-if you can add an exception in the configuration file for the blur effect to ignore kde-connect, you could keep the blurring effect and still use the pointer feature
I don't know if this is possible, nor am i experienced enough to know how to do it, but ill play around with it this weekend