Hi aris,
Yes you can make it default but you have to customize the code. Before making any changes in the code first of all you need to create a child theme and then only customize the code so that your updated version will not lose the code.
You go to the theme folder -> inc -> structure -> content-extension.php on line no 87 can you see this functions
if ( ! function_exists( 'ultimate_theloop_for_archive' ) ) :
If yes then can you see this line no 134 to 143, you will find this code.
<?php
if( has_post_thumbnail() ) {
$image = '';
$title_attribute = apply_filters( 'the_title', get_the_title( $post->ID ) );
$image .= '<figure class="post-featured-image">';
$image .= '<a href="' . get_permalink() . '" title="'.the_title( '', '', false ).'">';
$image .= get_the_post_thumbnail( $post->ID, 'featured', array( 'title' => esc_attr( $title_attribute ), 'alt' => esc_attr( $title_attribute ) ) ).'</a>';
$image .= '</figure><!-- .post-featured-image -->';
echo $image;
} ?>
Replace above code and add this below code
<?php
if( has_post_thumbnail() ) {
$image = '';
$title_attribute = apply_filters( 'the_title', get_the_title( $post->ID ) );
$image .= '<figure class="post-featured-image">';
$image .= '<a href="' . get_permalink() . '" title="'.the_title( '', '', false ).'">';
$image .= get_the_post_thumbnail( $post->ID, 'featured-medium', array( 'title' => esc_attr( $title_attribute ), 'alt' => esc_attr( $title_attribute ) ) ).'</a>';
$image .= '</figure><!-- .post-featured-image -->';
echo $image;
} ?>
and after doing this go to line no 238 and can you see this code if ( ! function_exists( ‘ultimate_theloop_for_single’ ) ) :
if yes then goto line no 276 to 287 and replace the old code and add the below code
<?php
if( has_post_thumbnail() ) {
$image = '';
$title_attribute = apply_filters( 'the_title', get_the_title( $post->ID ) );
$image .= '<figure class="post-featured-image">';
$image .= '<a href="' . get_permalink() . '" title="'.the_title( '', '', false ).'">';
$image .= get_the_post_thumbnail( $post->ID, 'featured-medium', array( 'title' => esc_attr( $title_attribute ), 'alt' => esc_attr( $title_attribute ) ) ).'</a>';
$image .= '</figure><!-- .post-featured-image -->';
echo $image;
} ?>
Hope this may help you
Thank you!