Thank you for the kind words about OpenSearch.
This and similar issues are tracked in https://github.com/opensearch-project/OpenSearch/issues/693
. Please take a look and comment on https://github.com/opensearch-project/OpenSearch/pull/814
that attempts at resolving it. Generally, we are doing our best to keep OpenSearch 1.0 backwards compatible with ES 7.10.2, see https://opensearch.org/faq/#c3
. If you find any issue like this one where a xfes does not work against OpenSearch 1.0, please take the time to report it and we'll do our best to fix!
Moving past 1.0, XFES can check the "distribution" field in this response and do OpenSearch-compatible version checks if it wants to.