Sync the ratings of the Wordpress plugin "rate-my-post" with all polylang translated variants of it.

polylang-sync-rate-my-post.php

<?php
/**
 * @package polylang-sync-rate-my-post
 */
/*
Plugin Name: polylang-sync-rate-my-post
Plugin URI: https://gist.github.com/Tyxz/09ea3d4b205738be2a8b2b777892b62a
Description: Sync the ratings of the Wordpress plugin "rate-my-post" with all polylang translated variants of it. 
Version: 0.1
Author: Arne Rantzen 
Author URI: https://github.com/Tyxz
License: ???
Text Domain: polylang-sync-rate-my-post
*/
if ( ! defined( 'ABSPATH' ) ) {
	die;
}

function pll_sync_store_rating($post_id, $translation_id, $new_avg_rating, $new_vote_count, $submitted_rating) {
  // Update rating sum
  $new_ratings_sum = $submitted_rating;
  if ( $new_vote_count > 1) {
    $new_ratings_sum = get_post_meta($post_id, 'rmp_rating_val_sum', true);
  }
  // Store new sum in linked page
  if ( ! add_post_meta( $translation_id, 'rmp_vote_count', $new_vote_count, true ) ) {
    update_post_meta( $translation_id, 'rmp_vote_count', $new_vote_count );
  }
  if ( ! add_post_meta( $translation_id, 'rmp_rating_val_sum', $new_ratings_sum, true ) ) {
    update_post_meta( $translation_id, 'rmp_rating_val_sum', $new_ratings_sum );
  }
  if ( ! add_post_meta( $translation_id, 'rmp_avg_rating', $new_avg_rating, true ) ) {
    update_post_meta( $translation_id, 'rmp_avg_rating', $new_avg_rating );
  }
}

function pll_sync_after_vote( $post_id, $new_avg_rating, $new_vote_count, $submitted_rating ) {
  // Check if polylang is enabled and working
  if (function_exists('pll_languages_list') && function_exists('pll_get_post')) {
    // get data from switcher for current page
    $raw = pll_the_languages( array('post_id' => $post_id, 'raw' => 1));
    // parse trough supported languages
    foreach($raw as $key => $value) {
      if(!$value['current_lang']) {
        $translation_id = pll_get_post( $post_id, $value['slug']);
        pll_sync_store_rating($post_id, $translation_id, $new_avg_rating, $new_vote_count, $submitted_rating);
      }
    }
  }
}

add_action('rmp_after_vote', 'pll_sync_after_vote', 10, 4);