GET file:///E:/main-KPJ5OKOH.js net:ERR_FILE_NOT_FOUND
This kind of error usually happens when your index.html uses absolute paths to scripts, styles, etc., like /main-KPJ5OKOH.js. Electron will look of the file in the system's (or drive's) root directory. The same issue occurs when you have <base href="/"> in index.html, which seems to be inserted by Angular by default.
What you can do is setting the the base URL to something like . or ./ either in your angular.json, index.html, or via build flag:
ng build --base-href .
See also: