Oxygen Repeater Advanced Query

I hope this helps

I added comments to the WP_Query array below.

<?php 

// query
$the_query = new WP_Query(array(
    'post_type'         => 'event',  // (the post type / custom post type)
    'posts_per_page'    => -1,
    'meta_key'          => 'featured',  // (acf-field-name-NOT-label)
    'orderby'           => 'meta_value', // (Don't change)
    'order'             => 'DESC' // (or ASC or RAND)
));

?>
<?php if( $the_query->have_posts() ): ?>
    <ul>
    <?php while( $the_query->have_posts() ) : $the_query->the_post(); 
        
        $class = get_field('featured') ? 'class="featured"' : '';
        
        ?>
        <li <?php echo $class; ?>>
            <a href="<?php the_permalink(); ?>"><?php the_title(); ?></a>
        </li>
    <?php endwhile; ?>
    </ul>
<?php endif; ?>

<?php wp_reset_query();  // Restore global post data stomped by the_post(). ?>

https://www.advancedcustomfields.com/resources/orde-posts-by-custom-fields/

tech