By your defdinition, life is obviously a computation.

The symbolic nature of digital computers is our interpretation on top of physical "problems". If we attribute symbols to the proteins encoded by DNA, symbolic computation takes place. If we don't attribute symbols to the voltages in a digtal computer, we could equally dismiss them as not being computers.

And we have a history of analogue computers as well, e.g. water-based computation[1][2], to drive home that computers are solving physical problems in the process of producing what we then interpret as symbols.

There is no meaningful distinction.

The question of whether life is a computation hinges largely on whether life can produce outputs that can not be simulated by a Turing complete computer, and that can not be replicated by an artificial computer without some "magic spark" unique to life.

Even in that case, there'd be the question of those outputs were simply the result of some form of computation, just outside the computable set inside our universe, but at least in that case there'd be a reasonable case for saying life isn't a computation.

As it is, we have zero evidence to suggest life exceeds the Turing computable.

[1] https://en.wikipedia.org/wiki/Water_integrator

[2] https://news.stanford.edu/stories/2015/06/computer-water-dro...