Dwelling Upon Seeming Levels of Emptiness? Note: the term sunyata here is being used from the Mahayana context.
Not too long ago, I asked this question about concentration and openness where I suggested that concentration was a hindrance to my practice. I received an answer which informed my intuitive understanding by @Andrei Volkov, in which he recommended a book called The Relaxed Mind by Dza Kilung Rinpoche. This changed my practice and opened up a new discernment concerning space, time and consciousness - essentially the aggregates and their ever subtle perceptions. It also led me to the Tibetan master Chogyam Trungpa who also adopts this same openness method.
Thus, shifting my practice to openness (as opposed to strict focus on a single object) I've been noticing a different kind of &quot;not-there-ness&quot;. To put this another way: the perception of body as it is normally known is no longer there, but I am still able to function perfectly fine - actually better in terms of how worldly things normally affect me.
It's most noticeable when sitting with people and when they are talking to me. There's a part of my mind that thinks, &quot;who is this person talking to?&quot; because, even though they are looking at me, it is like they are speaking into empty space, like they are in the room by themselves.
Please be clear: what I have described above is NOT the negation of suffering which should become clearer from the following.
I'm not able to reference the aggregates as they usually operate, but I discern that there is the perception of &quot;not-there-ness&quot; which presents as an extremely fine notion of space. However, that space-perception seems to have a definitive location situated where the body was previously and conventionally seen as solid matter giving rise to some sort of here-ness, and thus it's opposite: there-ness.
The form aggregate has taken another blow, but the feeling/perception aggregate has just dropped into a more refined level and thus is still able to create clinging to the idea of &quot;space-body&quot; because space-body has a very subtle pleasantness. In Theravada this might be known as arūpa-rāga: craving for immaterial existence thus perpetuating the consciousness aggregate in its entirety. It took me a while to see this, and I could only see it by opening my practice from where I was able to gain situational understanding or a bigger picture.
Here in these regions, it seems the motions of samsara cleverly uses indirect methods to sustain the samsaric body. I guess it can only operate at its current level of awareness, and if that level of awareness is largely formless then its movements should naturally reflect the subtleties of formlessness. Therefore, from a Mahayana perspective, I cannot see this as form is emptiness and emptiness is form. I cannot see this as sunyata. However, it may offer promise, but in ways that are now counter-intuitive.
My question is a little obscure, but I think it has some relevance:

Having studied sutta after sutta and read various works of the
masters, I'm making a reasoned observation that the enlightened mind
knows it is liberated, that it knows sunyata, but to what extent is that knowing not of the self such that one can know sunyata?
There always appears to be a claimant to the ever emerging subtleties
of emptiness rendering the idea of ending suffering a fallacy.

After nearly five years of intensive lay practice I'm getting quite tired of it all and find myself practising less and less. Although this is more helpful than a hindrance.
NOTE: I'm not sure if the term space-body is associated with any school. I've just used it spontaneously and completely impromptu. If it does have such an association, it may not share the same conceptual understanding with regard to the context of this question.
Impermanence is unsatisfactory. Chasing impermanence leads to suffering. What then should be known as known?
To this point, the Venerable Sariputta teaches:

DN34:1.3.23: What two things should be produced?
DN34:1.3.24: Two knowledges:
DN34:1.3.25: knowledge of ending, and knowledge of non-arising.
DN34:1.3.27: What two things should be directly known?
DN34:1.3.28: Two elements:
DN34:1.3.29: the conditioned element and the unconditioned element.

The conditioned and unconditioned elements are known by their characteristics:

AN3.47:0.3: 47. Characteristics of the Conditioned
AN3.47:1.1: “Mendicants, conditioned phenomena have these three characteristics.
AN3.47:1.2: What three?
AN3.47:1.3: Arising is evident, vanishing is evident, and change while persisting is evident.
AN3.47:1.4: These are the three characteristics of conditioned phenomena.”
AN3.47:2.0: Characteristics of the Unconditioned
AN3.47:2.1: “Unconditioned phenomena have these three characteristics.
AN3.47:2.2: What three?
AN3.47:2.3: No arising is evident, no vanishing is evident, and no change while persisting is evident.
AN3.47:2.4: These are the three characteristics of unconditioned phenomena.”

These characteristics guide the knowing.
Knowing is informed by perception. Perceiving the form of a cup, one perceives simultaneously the emptiness within. They are one and the same. By relinquishing form, emptiness necessarily grows as described in MN121:

MN121:12.5: There is only this that is not emptiness, namely that associated with the six sense fields dependent on this body and conditioned by life.’
MN121:12.6: And so they regard it as empty of what is not there, but as to what remains they understand that it is present.
MN121:12.7: That’s how emptiness is born in them—genuine, undistorted, and pure.
MN121:13.1: Whatever ascetics and brahmins enter and remain in the pure, ultimate, supreme emptiness—whether in the past, future, or present—all of them enter and remain in this same pure, ultimate, supreme emptiness.