I want to add the kernel version of the host to the filebeat output. Can I do that with this version, and if so, where in the config file do I need to add parameters.
Take a look at processors, e.g. this one: https://www.elastic.co/guide/en/beats/filebeat/current/add-process-metadata.html . I'm not sure if there is one that provides the kernel version and similar host information, but you can pass it through process env values.