Your list has its sources commented out (#), that’s why apt is not taking it into account.
That being said, self-hosting Zammad is not trivial. Even if you get professional services, they won’t (and can’t) teplace missing know-how on your operating system. If you feel overwhelmed by Linux and such, you might want to consider using Software as a Service instead.
Please don’t get me wrong, I’m not saying you can’t learn nor make it. If this is a public service, it potentially can get “dangerous” at some point.
Thanks MrGeneration for your solution and suggestion. There seem to be further problems with certificates, so the time has come for some professional maintainance.
We are running Zammad for about five years now. It is hosted internally as an IT and Facility Management ticket system. Thanks to the great product it has been as success story since day one. I think at that time something has not been available in the not self hosted version, maybe the LDAP integration.
But I will surely have a chat with the Zammad technician on what possibilities we have to improve our system.