I now made it so that the area where tessellation get’s applied is quite a bit bigger than the are where displacement get’s applied, so this removes most of the cracks. There are still some cracks visible, though they are only single pixels and with enabled Temporal AA they get blurred out and are no longer visible. But why are there cracks at all with “Crack free displacement” checked?
Where should I enter a tiling factor in the TexCoord node? It’s default to 1 in U and V and I did not change it. For the LandscapeCoords I also used the default values. Have you ever made tesselation on a landscape work with not using the Worldposition-XY node for the UVs? For flat surfaces using the Worldposition-XY for UVs is fine, but for angular surfaces it looks not nice, so if possible I would like to use the regular UV node.
Thanks a lot for your help, at least it is working now 