I get that, but there's no need to complicate things unnecessarily.

I'll make an even stronger claim, that biological brains are not only computers, but that they operate in binary, as well. Active and inactive - the mechanisms that trigger activation are incredibly nuanced and sophisticated, but the transfer of information through the network of biological neurons is a matter of zeroes and ones. A signal happens, or doesn't. Intensity, from a qualia persepective, ends up being a matter of frequency and spread, as opposed to level of stimulation. That, in conjunction with all sorts of models of brain function, is allowing neuroscience to make steady, plodding progress in determining the function and behavior of different neurons, networks, clusters, and types in the context in which they are found.

All else being equal, at the rate neuroscience is proceeding, we should be able to precisely simulate a human brain, in functionally real-time, using real brain networks as models, by around 2040. We should have a handle on every facet of brain chemistry, networking, electrical signaling, and individual neuronal behavior based on a comprehensive and total taxonomy of feature types down to the molecular level.

Figure out the underlying algorithms and you can migrate those functional structures to purely code. If you can run a mind on code, then it doesn't matter whether you're executing a sequence of computations in a meat brain, in a silicon chip, or using a billion genetically engineered notebook monkeys to painstakingly and tediously do the computations and information transfer manually, passing sheets of paper between them. ( the monkeys, of course, could not operate in real time.)

There won't be another significant phase change, like we saw from hydraulics to computation equivalence. Computation is what it actually, physically is, at the level of electrical signals and molecular behaviors. It's just extremely complex and sophisticated and elegantly interwoven with the rest of the human organism.

Brain gut interactions aren't necessary for human subjective experience or cognition. You could remove your brain entirely from your skull, while maintaining a equivalent level of electrical and chemical signaling from an entirely artifical platform of some sort, and as long as the interface between the biological and synthetic maintains the same signaling frequency, chemistry, and connectivity, then it doesn't matter what's on the synthetic end.

There are independently intelligent aspects to things like the gut biome, and other complex biological systems. Those aren't necessary for brains to do what brains do, except in a supportive role. Decouple the nutrition and evolutionary drives from the mind, and you're left with a fairly small chunk of brain - something like 5B neocortical neurons is the bare minimum of what you'd need to get human level intelligence. Everything on top of that is nice to have, but not strictly necessary from a proof of concept perspective.