For an example see the bottom of the page https://mydemoversion8-sandbox.mxapps.io/p/draganddrop

For a look at the code, download the project from Github:https://github.com/TimvanSteenbergen/MyDemoVersion8

The reactkanban does show the data correctly, and it looks like drag-and-drop is working, but dropping a card does not change the underlying data in Mendix.