To display the full feature image in Divi blog extras: Grid Extended add the below CSS code:

.el-dbe-blog-extra .entry-featured-image-url img {
    object-fit: fill !important;
}

1. For Page-Specific Changes:
   • Add the code into the page settings, typically in the custom CSS area for that specific page.
     
2. For Site-Wide Changes:
   • Navigate to the Divi Theme Options.
   • Go to the Custom CSS area.
   • Add the code into the Custom CSS box.