the essence of a thing or that thing in itself

I'd contend that both are actually the same thing. However that's metaphysics which I have a severe dislike for (as in: it's pointless) so maybe that's why I lump it all up in one thing, and in any case, however that may be: You will find neither of them in any model, anywhere. It's the very nature of a model to not be the thing itself.

I'm quite sure you'll say "yes" when I ask whether you understand the difference between map and territory. Is that understanding you have of that, however, on the level of the map, or on the level of the territory?

Those are the actually tough nuts to crack when rooting models, when fishing for axioms to ground things with. To understand the shape of the wall Plato's shadows get cast on, so that you know how the structure of the wall influences their shape, to be a giant iota closer to understanding.

It would, indeed, be a shame if being a Hegelian meant regressing the "know thyself" aspect to far behind what the Stoics had already figured out in spades.

indicates to me that our disagreement is not at the level of cybernetics, but at the level of what causes such interactions at all

Is that important? Is it not more important to identify and characterise interactions? Physicists with different beliefs about the ultimate mechanics of quantum uncertainty get along just fine. Personally, as already alluded to with metaphysics, I'm happy to say "yeah whatever causes that, causes that", I have no need or desire for distinctions beyond the measurable.