Zammad is a helpdesk system, which allows you to work on customer requests with multiple persons. However the installation is a bit tricky…
Use a plain Linux system, if Plesk is installed it will not work (at least not without serious pain)
When installing elastic search at least on Ubuntu, it will be required to regenerate the keystore. Delete /etc/elasticsearch/elasticsearch.keystore and then run “/usr/share/elasticsearch/bin/elasticsearch-keystore create”