This looks like a great start. I didn't find anything other than a couple of rocks that I could interact with, but it was fun to traverse the environment with the ball's different sizes.
The grass has some lines across the top of its planes - I think this might be being caused by the grass texture being set to repeat in its import settings, and that line is the bottom of the texture anti-aliased onto the top when mipmaps are created.
Hope you've had positive experiences using Godot, and thanks for doing a Linux build!