Override RenderCallback from LatestPosts

You certainly can do (not recommended). I just dig into the source there’s no filter/action hooks used in register_block_type() and it’s related classes. The only way (WordPress 5.3) is to redefine the latest post block again within your theme or plugin. The best way will be creating your custom blocks.

// Remove the existing action
remove_action( 'init', 'register_block_core_latest_posts', 10 );
your_render_callback( $attributes ) {...}
function register_block_core_latest_posts_wpse353682() {
    register_block_type(
        'core/latest-posts',
        'attributes' = [...], // copy attributes from the original function...
        'render_callback' => 'your_render_callback',
    );
}
// Re-attach the block
add_action( 'init', 'register_block_core_latest_posts_wpse353682' );