I’m not sure if thiis is the correct category to post this, but I couldn’t find information about an auto-discovery feature. Does Icinga have one similar to what Zabbix has?
No, Icinga does not have an auto discovery feature.
To achieve that, most implementation use a CM to create and remove hosts and services , you can see the options in github
There are more solutions that can be founds, but these are the official ones maintained by Icinga.