featured image from external sources

It needs some custom code. Here is an example

add_filter( 'wptelegram_p2tg_featured_image_source', function ( $source, $post ) {

  $image_url = get_post_meta( $post->ID, 'YOUR_IMAGE_URL_META_KEY', true );

  return $image_url;
}, 10, 2 );

It’s just an example code, not the actual working code.