Looks like that error is coming from Elasticsearch, but it's possible it's caused by something that Kibana is try to do. Seems like it's been happening for a while as well, all the way back to 4.4/2.2: Custom format isn't supported
I'm not sure why it would work locally for you but not in Cloud. Can you share any customizations you have in your config/elasticsearch.yml and config/kibana.yml files in your local installation?