I have created an index in ECE using filebeat as well as logstash. I am able to see the index in kibana in elasticseacrh index management. However, not able to create index pattern as the the indices are not available when I click the button to create it.
Indices only show up in the "Define index pattern" wizard if they have at least 1 document. Does your filebeat-* indices contain any documents?
If so, please share a HAR capture from your browser when trying to define an index pattern.