One other really awesome open source project is called Zammad. It is a source model similar to N8N for support and ticketing similar to ZenDesk, it’s very good looking, powerful, and a great platform overall
It features flexible data models, SMS, O365 integrations, and a ton more. It is a very powerful platform and worthwhile to work on!
Oh, they are ALSO out of Berlin 
You guys may be able to meet up
I´ve already talk about this fantastic project with @jan, we are also interested in this integration.
Should be similar to ZenDesk…but Zammad are located in Germany 
+1
Zammad is brilliant. Would be great to be able to automate the creation of tickets from different sources using n8n and also trigger actions when certain conditions are met for tickets, or if a chat comes in for instance.
Zammad web chat posting to Mattermost would be really cool.
We developed this as a custom module: https://www.npmjs.com/package/@digital-boss/n8n-nodes-zammad. As far as I remember it mirrors the complete API, except for the CTI endpoints at this time.
Zammad integration looks good. However one good addition will be putting filter to tickets.