Since iOS 15 / macOS 12 we can now add shaders in RealityKit 🎉 The entry point for these is GeometryModifier and SurfaceShader. The usage of these is used in the Underwater code sample: Building an Immersive Experience with RealityKit

Sounds like you might want to change the properties in PhysicsMassProperties for your object when it's in dynamic mode, maybe your impulse isn't big enough.

Try using HasModel instead of ModelEntity. Your best bet at solving this is putting a breakpoint after setting map and having a look at the contents with Xcode's inspector.