Display the featured image with the alt tag using get_the_post_thumbnail_url();

index.php

/**
 * To display the featured image with the alt tag 
 * 
 * @link: https://developer.wordpress.org/reference/functions/get_the_post_thumbnail_url/
 * @author: https://profiles.wordpress.org/thelilmercoder/
 */

$thumbnail = get_the_post_thumbnail_url();
 
if ( $thumbnail ) {
    $alt_text = get_post_meta( $thumbnail->ID, '_wp_attachment_image_alt', true );
 
    if ( ! empty( $thumbnail ) ) {
        if ( ! empty( $alt_text ) ) {
            $alt_text = $alt_text;
       } else {
            $alt_text = __( 'no alt text set', 'textdomain' ); 
       }
       echo '';
   }
}