Elastic have deprecated generating Custom Beats. I’m not surprised by the move; signals showed that the project was barely a labour of love for Elastic.
I mentioned in my guide to generating a custom Beat that the documentation was in poor shape and PRs weren’t being reviewed very quickly. I opened two PRs and each took over a year to be reviewed.
The custom Beat I wrote to bring data from Cisco ACI to Elasticsearch/Logstash is in the process of being rewritten. I will write about that experience when it’s complete.