There are of course many ways to ingest data in to Elasticsearch but the recommended way for many Observability use cases would be Beats. We have a recipe how to set up Filebeat and Metricbeat with ECK in our recipes section in the Github repository.
The upcoming release of ECK 1.2 will improve the situation further by supporting Beats as first class component in ECK. You can take a sneak peak at what is coming in our pre-release docs.
Of course you can run Logstash as well but you would have to setup the connection to the Elasticsearch cluster managed by ECK yourself. We have an official Helm chart for Logstash that can get you started.