If understood correctly, the Project Chrono (PCh) is a collection of several libraries that tackle specific situations in body dynamics. Accordingly, the coupling of a SPH solvers with PCh means, concretely, the individual coupling with such component libraries.
From the list in the Feature pages https://www.gpusph.org/features/ I gather the following functionalities have been implemented:
Floating objects Objects with joints Moving objects (imposed motion) Collision detection Planes
If the question makes sense, would it be possible to know a more specific list of PCh libraries that have been linked with GPUSH? Are these native libraries connected to GPUSPH with open-source wrappers?