rasidagac

The following code works for me

add_filter( 'woocommerce_related_products', 'related_products_by_attribute', 10, 3 );
function related_products_by_attribute( $related_posts, $product_id, $args ) {
    $taxonomy   = 'pa_sezon'; // HERE define the targeted product attribute taxonomy
    $term_slugs = wp_get_post_terms( $product_id, $taxonomy, ['fields' => 'slugs'] ); // Get terms for the product
    if ( empty($term_slugs) )
        return $related_posts;
    $posts_ids = get_posts( array(
        'post_type'            => 'product',
        'ignore_sticky_posts'  => 1,
        'posts_per_page'       => 4,
        'post__not_in'         => array( $product_id ),
        'tax_query'            => array( array(
            'taxonomy' => $taxonomy,
            'field'    => 'slug',
            'terms'    => $term_slugs,
        ) ),
		'meta_query'           => array( array(
            'key'     => '_stock_status',
            'value'   => 'instock',
            'compare' => '=',
        ) ),
        'fields'  => 'ids',
        'orderby' => 'date',
    ) );
    return count($posts_ids) > 0 ? $posts_ids : $related_posts;
}