Notice: Array to string conversion in /docroot/modules/contrib/feeds_para_mapper/src/Feeds/Target/WrapperTarget.php on line 297

I get two errors, maybe related

Notice: Array to string conversion in Drupal\feeds_para_mapper\Feeds\Target\WrapperTarget->getSummary() (line 283 of /modules/feeds_para_mapper/src/Feeds/Target/WrapperTarget.php)

and

LogicException: The database connection is not serializable. This probably means you are serializing an object that has an indirect reference to the database connection. Adjust your code so that is not necessary. Alternatively, look at DependencySerializationTrait as a temporary solution. in Drupal\Core\Database\Connection->__sleep() (line 1546 of /core/lib/Drupal/Core/Database/Connection.php)

The import fails using Drupal 8.8.x

Im getting the same issue, nothing will save in the mapping UI.

So currently this module doesn't work with anything great than 8.8.x.

I'm not sure how people are importing paragraphs without this module apart from creating separate feeds.

I haven't tested it yet (the field mapper doesn't respond after installing this module), but does this help?

Needs review

When applying the patch to 8-1.x branch, i get this code:

      if (isset($sum) && $sum instanceof TranslatableMarkup) {
        $final_str = $sum->getUntranslatedString();
        $final_str .= "<br>" . $temp_sum;
        $args = $sum->getArguments();
        if (isset($args)) {
          $final_str[] = $this->t($final_str, $args);
        }

$final_str .= "<br>" . $temp_sum;
makes it a string, and then
$final_str[] = $this->t($final_str, $args);
treats it as an array? That gives an `[] operator not supported` error.

A simpler solution perhaps is to convert $sum to string if it's an array when it's being created.

 $sum = is_array($sum) ? implode(PHP_EOL, $sum) : $sum;