How to include thumbnail images in Wordpress RSS feeds

wordpress_thumbnails_in_rss_feed.php

/* 
   By default Wordpress does not include post thumbnails in RSS feeds.
   
   To enable:
   1. Open your Wordpress theme's functions.php file located in /wp-content/themes/[YOUR THEME]/
   2. Paste the code snippet below into your functions.php
   3. Save to have the changes take effect.
   
*/

function thumbnails_in_feeds( $content ) {
  
    global $post;
  
    if( has_post_thumbnail( $post->ID ) ) {
      
        $content = '<p>' . get_the_post_thumbnail( $post->ID , 'medium_large') . '</p>' . $content;
      
    }
  
    return $content;
}

add_filter( 'the_excerpt_rss', 'thumbnails_in_feeds' );

add_filter( 'the_content_feed', 'thumbnails_in_feeds' );

Sample output here: