Locke was actually closer to Kant than what the latter typecast him as. That is, while denying that the mind came equipped with specific propositional content, Locke nevertheless did believe we are born with faculties for receiving and processing content delivered from experience. "Blank slate" has roots going back to the ancient Greeks and Islamic philosophers, but nothing much further happened with it till Locke seized the idea.
Animals exhibit a horde of behaviors and skills which aren't learned, so clearly narrow kinds of knowledge can be innate in the cognitive systems of agents -- not just the broad, "empty" conceptual structure of an operating system that needs to be there to begin with simply to apprehend and process new information.
But there's probably nothing innate in a mind/brain as literal propositional knowledge, although there may be innate syntactic templates. Which still require stimulation and reception from experience or sensory input to provide content and a specific language to manipulate (as well as to avoid the eventual atrophy of such pre-installed faculties if they go unused into late childhood). While the circuit relationships and stored states of an artificial computer's physical hardware can correspond to and be converted / translated back into the symbolic languages that its software was originally devised in the context of, it would be quite a a stretch to imagine evolution working with an underlying, formal language scheme as it haphazardly developed biotic brains over the ages.
Early philosophers were forced to resort to propositional activity as their "epistemic stuff" and conclusion-generation machine because that was the only practical medium for thinking and communicating -- as well as language providing abstraction and quasi-independence from the concrete world and its contingent entities, events, and circumstances. Scientists get to actually examine particulars and a posteriori matters (like a brain instead of mind; distinct beings instead of being-hood), but philosophy is traditionally concerned with the meta-levels or overarching principles and order that these localized particulars and activities conform to (or "ought" slash should conform to, when it's a prescriptive context).