How can a Mutual Fund that is not an ETF be traded on an exchange?

Have a look at https://www.onvista.de/fonds/DJE-Zins-Dividende-PA-EUR-Fonds-LU0553164731. It is the information page for a regular fund ("mutual fund"), not an ETF. Nevertheless, it has a dropdown box for choosing the exchange it is traded at, as well as the entry "KVG" (Kapitalverwaltungsgesellschaft, company which issues the funds).

How is it possible that this funds is traded at several exchanges?