Notice: Trying to access array offset on value of type bool in uc_quote_uc_order() (line 311

This resolved the problem for me. Thank you!

I got still some errors with PHP 8.2 and created a patch:

#9 is an improvement over #6, but it should be like this:

      $order->quote = (isset($quote) && is_array($quote)) ? $quote : array();
      $order->quote['accessorials'] = isset($quote['accessorials']) ? strval($quote['accessorials']) : '';

db_query()->fetchAssoc() returns FALSE if there is no quote in the table and returns an array with elements 'method', 'accessorials', and 'rate' if there is a quote.

So we don't need all these isset() and is_array() tests.

Please test this: