Is the CustomBrush_Landmass_River working in 4.25? I have been learning the landscaping tools and it seems like the river brush is broken.
Creating a flat landscape with the Landmass Plugin activated, activating the blueprint Brushes and selecting - CustomBrush_Landmass_River. Using the default settings, my terrain is offset 100units in Z. With no other effect coming from the river spline. The only setting that seems to change anything is the Brush Type.
Let me know if you need more information. I have tried all settings individually with no luck.The CustomBrush_Landmass works as expected.
EDIT : I am following the documentation here - Landscape Blueprint Brushes | Unreal Engine Documentation