My thesis is that the true ontology - the correct set of concepts by means of which to understand the nature of reality - is several layers deeper than anything you can find in natural science or computer science. The attempt to describe reality entirely in terms of the existing concepts of those disciplines is necessarily incomplete, partly because it's all about X causing Y but not about what X and Y are. Consciousness gives us a glimpse of the "true nature" of at least one thing - itself, i.e. our own minds - and therefore a glimpse of the true ontological depths. But rationalists and materialists who define their rationalism and materialism as "explaining everything in terms of the existing concepts" create intellectual barriers within themselves to the sort of progress which could come from this reflective, phenomenological approach.

I'm not just talking about arcane metaphysical "aspects" of consciousness. I'm talking about something as basic as color. Color does not exist in standard physical ontology - "colors" are supposed to be wavelengths, but a length is not a color; this is an example of the redefining of concepts that I mentioned in the previous long comment. This is actually an enormous clue about the nature of reality - color exists, it's part of a conscious state, therefore, if the brain is the conscious thing, then part of the brain must be where the color is. But it sounds too weird, so people settle for the usual paradoxical crypto-dualism: the material world consists of colorless particles, but the experience of color is in the brain somewhere, but that doesn't mean that anything in the brain is actually "colored". This is a paradox, but it allows people to preserve the sense that they understand reality.

You asked for a simple exposition but that's just not easy. Certainly color ought to be a very simple example: it's there in reality, it's not there in physics. But let me try to express my thoughts about the actual nature of color... it's an elementary property instantiated in certain submanifolds of the total instantaneous phenomenal state of affairs existing at the object pole of a monadic intentionality which is formally a slice through the worldline of a big coherent tensor factor in the Machian quantum geometry which is the brain's exact microphysical state... it's almost better just to say nothing, until I've written some treatise which explains all my terms and their motivations.

I only made my original comment because you spontaneously expressed perplexity at the nature of "sentience", and I wanted to warn you against the false solutions that most rationalist-materialists will adopt, under the self-generated pressure to explain everything using just the narrow ontological concepts they already have.