Analog systems are equally deterministic. In fact, a digital circuit is just an analog circuit where the interpretation of the voltages is quantized.

An analog radio tuned to read nothing but static is not deterministic.

Just because you can't determine what it will do doesn't mean that it's nondeterministic. You just don't have enough information about the hundreds of billions of radio sources scattered all throughout the galaxy. You probably don't have any better information about what the radio station a few kilohertz away will broadcast next, either.