Logstash create plugin tutorial

Hi,
I'am looking for good/updated ressources to learn how to create a codec-plugin.
I have tried to follow this one : How to write a Logstash codec plugin | Logstash Reference [8.4] | Elastic ( I used the plugin generator tool) but I find that it fast-tracks many aspects (inner workings of how the plugin works) and seems outdated (links are broken, warn messages are raised, ...).

Alas at the end the plugin fails to load (as shown in the logstash-plain.log) and yet /bin/logstash-plugin list shows the plugin...

I verified and yes the owner and permissions of my .gem file are correctly set.

Thanks

Best regards,

Laurent