Not seeing logs from OTEL Collector in APM

Elastic Observability
2 
  otlphttp/kibana:
    traces_endpoint: "http://10.0.1.158:8200"

should be

  otlphttp/kibana:
    traces_endpoint: "http://10.0.1.158:8200/v1/traces"

or

  otlphttp/kibana:
    endpoint: "http://10.0.1.158:8200"

When using endpoint the exporter automatically appends /v1/traces for traces.

The APM Server has a root API node which, unfortunately for this case, returns a 200 success when you POST against it:

curl -X POST http://127.0.0.1:8200/ \
  -H "Authorization: Bearer secret_token"

{
  "build_date": "2021-12-18T19:59:06Z",
  "build_sha": "24fe620eeff5a19e2133c940c7e5ce1ceddb1445",
  "publish_ready": true,
  "version": "8.17.2"
}

So I think what's happening is that the OTLP HTTP Exporter is getting a 200 response code when it POSTS the batch, which it thinks means the batch succeeded. So you get no feedback that something isn't working, and the traces never land in Elasticsearch.