I had the same problem. Maybe it would be helpful to specify the 'Mail System' module as a dependency in the .info.yml file?
Patch does not work for me. (Neither 3.0.0 nor 3.0.x-dev).
Simliar problem here when I try to update from Drupal 9 to Drupal 10.
PHP 8.1
Module-Version: 2.2.2
Error-Message on admin/config/services/mailchimp
GuzzleHttp\Exception\ConnectException: cURL error 6: Could not resolve host: .api.mailchimp.com (see https://curl.haxx.se/libcurl/c/libcurl-errors.html) for https://.api.mailchimp.com/3.0/connected-sites in GuzzleHttp\Handler\CurlFactory::createRejection() (line 210 of /usr/www/users/workflow/clemco/clemco8/vendor/guzzlehttp/guzzle/src/Handler/CurlFacto
For me worked to add in module/contrib/ckeditor/js/plugins/drupalmedia/plugin.js
dtd['p']['drupal-media'] = 1;
as proposed for same problem with drupalentity in:
https://www.drupal.org/project/entity_embed/issues/2892820#comment-12849509 →
No idea which side effects will occur ...