Remove accents from url slug before WordPress search for a post

functions.php

<?php

/**
 * Remove accents from url slug before WordPress search for a post
 *
 * When you access page with accents you will not find any posts because
 * WordPress is removing accents from url before saving it to database.
 * This function will remove accents from url before WordPress start looking
 * for post.
 *
 * @param $query WP_Query WordPress query
 *
 * @return WP_Query
 */
function motivast_remove_accents_from_url_slug( $query ) {

    /**
     * Parse query only for single page/post
     */
    if( $query->is_main_query() && $query->is_singular() ) { // is_singular works for any post type

        $name = $query->get('name'); // Get slug from url
        $name = urldecode( $name ); // Decode url to unicode
        $name = remove_accents($name); // Remove accents

        $query->set('name', $name); // Set new name to search posts by slug without accents
    }

    return $query;
}

add_filter('pre_get_posts', 'motivast_remove_accents_from_url_slug');