I’ve tried out a variety of surfaces.
Being a beach sprinter(surf lifesaving) I went through a phase of doing plyos on sand as that was what I raced on.
Apart from aggrivating my achilles, I also found that it was hard to really attack the surface thus defeating the point of the exercise.
I agree that grass gives a rebound with out too much impact. You relly want a good flat surface and no moisture though!!
if you’re not doing a high volume session though the track is still a good option with the grip and quick contact it gives