My sitemap is not available in other languages using Polylang

I have done steps 1, 2 and 3 but unfortunately it doesn’t seem to have made any difference

We don’t use a theme, so I don’t have the option to create the files described in the article.
But I’ve created a code snippet with the following code which doesn’t seem to have made any difference.

Please let me know if I’ve done it wrong.

use RankMath\Sitemap\Sitemap;

/**
 * Manages the compatibility with the Rank Math plugin
 *
 */
class PLL_RankMath {
    /**
     * Add specific filters and actions
     */
    public function init() {
        add_action( 'wp_loaded', [ $this, 'rm_translate_options_keys' ] );
        if ( PLL() instanceof PLL_Frontend ) {
            // Filters sitemap queries to remove inactive language or to get
            // one sitemap per language when using multiple domains or subdomains
            // because Rank Math does not accept several domains or subdomains in one sitemap
            add_filter( 'rank_math/sitemap/post_count/join', [ $this, 'rank_math_sitemap_join_clause' ], 10, 2);
            add_filter( 'rank_math/sitemap/post_count/where', [ $this, 'rank_math_sitemap_where_clause' ], 10, 2);
            add_filter( 'rank_math/sitemap/get_posts/join', [ $this, 'rank_math_sitemap_join_clause' ], 10, 2 );
            add_filter( 'rank_math/sitemap/get_posts/where', [ $this, 'rank_math_sitemap_where_clause' ], 10, 2 );

            if ( PLL()->options['force_lang'] > 1 ) {
                add_filter( 'rank_math/sitemap/enable_caching', '__return_false' ); // Disable cache! otherwise Rank Math keeps only one domain
                add_filter( 'home_url', [ $this, 'rank_math_home_url' ], 10, 2 );
            } else {
                add_filter( 'rank_math/sitemap/enable_caching', '__return_false' );
                // Get all terms in all languages when the language is set from the content or directory name
                add_filter( 'get_terms_args', [ $this, 'rm_update_term_query_args' ] );
                // Include links to homepage of all languages.
                add_filter( 'rank_math/sitemap/exclude_post_type', [ $this, 'update_sitemap_contents' ], 0 , 2 );
            }

            add_filter( 'pll_home_url_white_list', [ $this, 'rm_white_list_home_url' ] );
            add_filter( 'rank_math/frontend/canonical', [ $this, 'rm_home_canonical' ], 10, 1 );
            add_filter( 'rank_math/opengraph/facebook', [ $this, 'rank_math_alt_locales' ], 10 );
        } else {
            // Copy post metas
            add_filter('pll_copy_post_meta', [ $this, 'rm_sync_post_metas' ], 10, 4);
            // translate post metas
            add_filter( 'pll_translate_post_meta', [ $this, 'rm_translate_post_meta' ], 10, 3 );
            // Export post metas
            add_filter( 'pll_post_metas_to_export', [ $this, 'rm_export_post_metas' ], 10, 1 );
        }
    }

    /**
     * Register options keys for translation.
     *
     * @return void
     */
    public function rm_translate_options_keys() {
        // @TODO clear cache!

        // keys for rank-math-options-general option
        $keys = [
            'breadcrumbs_separator',
            'breadcrumbs_home_label',
            'breadcrumbs_archive_format',
            'breadcrumbs_search_format',
            'breadcrumbs_404_label',
            'content_ai_country',
            'content_ai_tone',
            'content_ai_audience',
            'content_ai_language',
            'toc_block_title',
        ];
        new PLL_Translate_Option( 'rank-math-options-general', array_fill_keys( $keys, 1 ), [ 'context' => 'rank-math' ] );

        // Keys for rank-math-options-titles
        $keys = [
            'knowledgegraph_name',
            'homepage_title',
            'author_archive_title',
            'date_archive_title',
            'search_title',
            '404_title',
            'pt_post_title',
            'pt_post_description',
            'pt_post_default_snippet_*',
            'pt_page_title',
            'pt_page_description',
            'pt_page_default_snippet_*',
            'pt_attachment_title',
            'pt_attachment_description',
            'pt_attachment_default_snippet_*',
            'pt_product_title',
            'pt_product_description',
            'pt_product_default_snippet_*',

        ];
        new PLL_Translate_Option( 'rank-math-options-titles', array_fill_keys( $keys, 1 ), [ 'context' => 'rank-math' ] );
    }

    /**
     * Updates the home and stylesheet URLs when using multiple domains or subdomains.
     *
     * @param string $url
     * @param string $path
     * @return $url
     */
    public function rank_math_home_url( $url, $path ) {
        $uri = empty( $path ) ? ltrim( (string) wp_parse_url( pll_get_requested_url(), PHP_URL_PATH ), '/' ) : $path;
        if ( 'sitemap_index.xml' === $uri || preg_match( '#([^/]+?)-sitemap([0-9]+)?\.xml|([a-z]+)?-?sitemap\.xsl#', $uri ) ) {
            $url = PLL()->links_model->switch_language_in_link( $url, PLL()->curlang );
        }

        return $url;
    }

    /**
     * Get the active languages.
     *
     * @return array list of active language slugs, empty if all languages are active
     */
    protected function rank_math_get_active_languages() {
        $languages = PLL()->model->get_languages_list();
        if ( wp_list_filter( $languages, [ 'active' => false ] ) ) {
            return wp_list_pluck( wp_list_filter( $languages, [ 'active' => false ], 'NOT' ), 'slug' );
        }
        return [];
    }

    /**
     * Modifies the sql request for posts sitemaps
     * Only when using multiple domains or subdomains or if some languages are not active
     *
     * @param string $sql       JOIN clause
     * @param string $post_type
     * @return string
     */
    public function rank_math_sitemap_join_clause( $sql, $post_type ) {
        return pll_is_translated_post_type( $post_type ) ? $sql . PLL()->model->post->join_clause( 'p' ) : $sql;
    }

    /**
     * Modifies the sql request for posts sitemaps
     * Only when using multiple domains or subdomains or if some languages are not active
     *
     * @param string $sql       WHERE clause
     * @param string $post_type
     * @return string
     */
    public function rank_math_sitemap_where_clause( $sql, $post_type ) {
        if ( ! pll_is_translated_post_type( $post_type ) ) {
            return $sql;
        }

        if ( PLL()->options['force_lang'] > 1 && PLL()->curlang instanceof PLL_Language ) {
            return $sql . PLL()->model->post->where_clause( PLL()->curlang );
        }

        $languages = $this->rank_math_get_active_languages();

        if ( empty( $languages ) ) { // Empty when all languages are active.
            $languages = pll_languages_list();
        }

        return $sql . PLL()->model->post->where_clause( $languages );
    }

    /**
     * When the language is set from the content or directory name, the language filter (and inactive languages) need to be removed for the taxonomy sitemaps.
     *
     * @param array $args get_terms arguments
     * @return array modified list of arguments
     */
    public function rm_update_term_query_args( $args ) {
        if ( isset( $GLOBALS['wp_query']->query['sitemap'] ) ) {
            $args['lang'] = implode( ',', $this->rank_math_get_active_languages() );
        }
        return $args;
    }

    /**
     * A way to apply rank_math/sitemap/{$type}_content for all indexable post types.
     *
     * Updates homepage and archive pages to include links to the active languages.
     *
     * Always returns $excluded without altering it's value.
     * @param $exclude
     * @param $type
     * @return mixed
     */
    public function update_sitemap_contents( $exclude, $type ) {
        if ( pll_is_translated_post_type( $type ) && ( 'post' !== $type || ! get_option( 'page_on_front' ) ) ) {
            // Include post, post type archives, and the homepages in all languages to the sitemap when the front page displays posts get_ogp_alternate_languages() !
            \add_action( "rank_math/sitemap/{$type}_content", function() use( $type ) {
                $generator = new \RankMath\Sitemap\Generator();
                $post_type_obj = get_post_type_object( $type );
                $languages = wp_list_filter( PLL()->model->get_languages_list(), [ 'active' => false ], 'NOT' );
                $mod       = Sitemap::get_last_modified_gmt( $type );
                $output    = '';
                if  ( 'post' === $type ) {

                    if ( ! empty( PLL()->options['hide_default'] ) ) {
                        // The home url is of course already added by WPSEO.
                        $languages = wp_list_filter( $languages, [ 'slug' => pll_default_language() ], 'NOT' );
                    }

                    foreach ( $languages as $lang ) {
                        $output .= $generator->sitemap_url([
                            'loc' => pll_home_url( $lang->slug ),
                            'mod' => $mod
                        ]);
                    }
                }

                elseif ( $post_type_obj->has_archive ) {
                    // Exclude cases where a post type archive is attached to a page (ex: WooCommerce).
                    $slug = true === $post_type_obj->has_archive ? $post_type_obj->rewrite['slug'] : $post_type_obj->has_archive;

                    if ( ! wpcom_vip_get_page_by_path( $slug ) ) {
                        // The post type archive in the current language is already added by WPSEO.
                        $languages = wp_list_filter( $languages, [ 'slug' => pll_current_language() ], 'NOT' );
                        foreach ( $languages as $lang ) {
                            PLL()->curlang = $lang; // Switch the language to get the correct archive link.
                            $output .= $generator->sitemap_url([
                                'loc' => pll_home_url( $lang->slug ),
                                'mod' => $mod
                            ]);
                        }
                    }
                }
                return $output;
            });
        }
        return $exclude;
    }

    /**
     * Include language code in the canonical URL.
     *
     * @param string $canonical The canonical URL.
     *
     * @return mixed|string
     */
    public function rm_home_canonical( $canonical ) {
        if ( ! is_home() ) {
            return $canonical;
        }

        $path = ltrim( (string) wp_parse_url( pll_get_requested_url(), PHP_URL_PATH ), '/' );
        return $canonical . $path;

    }

    /**
     * Filters home url.
     *
     * @param array $arr
     * @return array
     */
    public function rm_white_list_home_url( $arr ) {
        return array_merge( $arr, [  [ 'file' => 'seo-by-rank-math' ]  ] );
    }

    /**
     * Updates OpenGraph meta output by adding support for translations.
     *
     * @return void
     */
    public function rank_math_alt_locales() {
        $og = new \RankMath\OpenGraph\OpenGraph();
        $og->network = 'facebook';
        foreach ( $this->update_ogp_alternate_languages() as $lang ) {
            $og->tag('og:locale:alternate', $lang );
        }
    }

    /**
     * Get alternate language codes for Opengraph.
     *
     * @return string[]
     */
    protected function update_ogp_alternate_languages() {
        $alternates = [];

        foreach ( PLL()->model->get_languages_list() as $language ) {
            if ( isset( PLL()->curlang ) && PLL()->curlang->slug !== $language->slug && PLL()->links->get_translation_url( $language ) && isset( $language->facebook ) ) {
                $alternates[] = $language->facebook;
            }
        }
        // There is a risk that 2 languages have the same Facebook locale. So let's make sure to output each locale only once.
        return array_unique( $alternates );
    }

    /**
     * Synchronizes or copies the metas.
     *
     * @param $metas
     * @param $sync
     * @param $from
     * @param $to
     * @return array
     */
    public function rm_sync_post_metas( $metas, $sync, $from, $to ) {
        if ( ! $sync ) {
            $metas = array_merge( $metas, $this->rm_translatable_meta_keys() );
            // Copy image URLS
            $metas[] = 'rank_math_facebook_image';
            $metas[] = 'rank_math_facebook_image_id';
            $metas[] = 'rank_math_twitter_use_facebook';
            $metas[] = 'rank_math_twitter_image';
            $metas[] = 'rank_math_twitter_image_id';

            $metas[] = 'rank_math_robots';

        }

        $taxonomies = get_taxonomies([
            'hierarchical' => true,
            'public'       => true,
        ]);

        $sync_taxonomies = PLL()->sync->taxonomies->get_taxonomies_to_copy( $sync, $from, $to );

        $taxonomies = array_intersect( $taxonomies, $sync_taxonomies );
        foreach ( $taxonomies as $taxonomy ) {
            $metas[] = 'rank_math_primary_' . $taxonomy;
        }

        return $metas;

    }

    /**
     * Translate the primary term during the synchronization process
     *
     * @param int    $value Meta value.
     * @param string $key   Meta key.
     * @param string $lang  Language of target.
     *
     * @return int
     */
    public function rm_translate_post_meta( $value, $key, $lang ) {
        if ( ! \MyThemeShop\Helpers\Str::starts_with( 'rank_math_primary_', $key) ) {
            return $value;
        }

        $taxonomy = str_replace( 'rank_math_primary_', '', $key );
        if ( ! PLL()->model->is_translated_taxonomy( $taxonomy ) ) {
            return $value;
        }

        return pll_get_term( $value, $lang );
    }

    /**
     * Meta key with translatable values.
     *
     * @return string[]
     */
    private function rm_translatable_meta_keys() {
        return [
            'rank_math_title',
            'rank_math_description',
            'rank_math_facebook_title',
            'rank_math_facebook_description',
            'rank_math_twitter_title',
            'rank_math_twitter_description',
            'rank_math_focus_keyword',
        ];
    }

    /**
     * Rank math translatable metas to export.
     *
     * @param array $metas
     *
     * @return string[]
     */
    public function rm_export_post_metas( $metas ) {
        $rm_metas = array_fill_keys( $this->rm_translatable_meta_keys(), 1 );
        return array_merge( $metas, $rm_metas );
    }
}

add_action(
    'plugins_loaded',
    function() {
        if ( defined( 'RANK_MATH_VERSION' ) && class_exists( 'PLL_Integrations' ) ) {
            add_action( 'pll_init', array( PLL_Integrations::instance()->rankmath = new PLL_RankMath(), 'init' ) );
        }
    },
    0
);

Thanks Kolja! Worked perfectly