I got this from a raw vegan food forum. I have seen to use cauliflower that
has been finely chopped in the food processor as a substitute for rice.
I've also seen to use turnips or rutabaga, but I felt those things would be
too strongly flavored for my liking. At least as a rice substitute.

But recently, someone tried it with cucumber and said it worked really well.
He didn't peel his. Just processed it until it resembled rice. He did it
up with a faux cheese sauce and Mexican seasonings.