Hi Volker,
Thanks for contacting Syncfusion support.
We have prepared a sample to read out the card details from cardClick and DragStop events and the same can be available in following link.
Sample: https://www.syncfusion.com/downloads/support/forum/157933/ze/SfKanbanGetArgs1077748655
Currently we need to Deserialize the arguments in application end, Since it is an object type. Also, we considered this as defect and we logged the below defect report. The fix for this defect will be included in out upcoming volume 3 release which is expected to roll out on end of September 2020. We would appreciate your valuable patience. You can track the status through the below feedback link.
Feedback Link: https://www.syncfusion.com/feedback/18029/getting-object-type-in-args-value-for-dragstop-and-cardclick-event-of-kanban
Kindly try the above sample and get back to us, If you need further assistance.