Hi @yago82,
Are you trying to send Metricbeat data directly into OpenSearch? Beats does a version check to make sure that it is connecting to Elasticsearch. If you want to send traffic from Beats over to OpenSearch, you’ll want to do that via Logstash using the OpenSearch Logstash Output plugin. You can find more information on the agents and ingestion tools documentation page.
Another option would be to use another open source agent like Fluent Bit and send that into OpenSearch. Anurag from Calytpia wrote a blog post on doing just that.
Hope that helps.