Translate media automatically when using Polylang in Wordpress

auto-polylang-media.php

<?php 

if ( !function_exists( 'translate_all_media' ) ) {
  function translate_all_media() {
    global $polylang;

    if(!$polylang) return;

    // find languages
    $langs = array();
    foreach (pll_languages_list() as $lang){
      if(pll_default_language() !== $lang){
        $langs[] = $lang;
      }
    }
    
    // find media
    $posts = get_posts(array(
      'post_type'      => 'attachment',
      'posts_per_page' => -1,
      'lang'           => pll_default_language(),
    ));

    $int = 0;
    foreach ($posts as $post) {
      // itterate over all langs
      foreach ($langs as $new_lang) {
        // Bails if the translations already exists
        if ( ! $polylang->model->post->get_translation( $post->ID, $new_lang ) ) {
          $int++;
          // creates the translation
          $polylang->posts->create_media_translation( $post->ID, $new_lang );
        }
      }
    }
    
    // notify admin
    if($int > 0){
      echo '<div class="notice notice-success is-dismissible"><p>';
      echo 'Translated '.$int.' media';
      echo '</p></div>';
    }
  }
  add_action( 'admin_notices', 'translate_all_media' );
}

I had recently the same issue
You need to replace $polylang->filters_media->create_media_translation( $post->ID, $new_lang ); by $polylang->posts->create_media_translation( $post->ID, $new_lang );. I found the solution into the file /polylang-pro/modules/plugins/acf.php line 429

Thanks!

Excellent!
I wonder why the "if(pll_default_language() !== $lang)" con is needed when populate the $langs array beforehand...
I've noticed that loading an image from inside a post in DEFAULT language, it works (i.e.: the media library updates with the loaded attachment post fro all the languages available); but if you load an image from a post of an ALTERNATIVE language (not DEFAULT), the media library doesn't not automatically translate.
However, knowing that, it works like a charm!