OpenSearch Dashboard mapping conflicts and OpenSearch mapping conflicts are not the same.

OpenSearch mappings are built from the OpenSearch templates, for fields that don't have settings specified in the templates, the mappings are created dynamically from the data you send in. A mapping conflict occurs when you try to send data into a field that already has a mapping created but the data doesn't meet the same type (date, integer, string, etc.)

OpenSearch Dashboards mapping conflicts occur when the fields don't match the type saved in the index pattern. This can be fixed by updating the index pattern field list.
This can be found in 

Then click on the rotating arrows in the top right corner.