Cannot confirm deprecation log on K8S deployment or docker


I'm operating Elasticsearch 7.17.9 on K8S using the ECK.

I'm trying to review the deprecation log which is documented here Logging | Elasticsearch Guide [7.17] | Elastic as I'm planning to upgrade our Elasticsearch to version 8.

But for some reason, I cannot confirm any deprecation log message for our cluster even after calling a deprecated API like GET /_xpack/license.

I've also tested with the 7.17.9 docker image but the result is the same, no deprecation log in the STDOUT.

From my understanding, both K8S deployment (managed by ECK) and docker are configured to emit deprecation logs to STDOUT by default so I'm checking STDOUT outputs. But I've also checked the log directory, just in case, and found only the gc logs.

How can I enable (it is enabled by default if I'm correct) and confirm the deprecation log on K8S deployment (or docker)?