The word phenomenon too strongly suggests a speculative approach to knowledge.
Internomenon might be better.
We know reality not by sensing it and recording what we sense in our minds. We participate in reality and interact with fellow beings within reality, and these interactions are what we know. We come to know more about both our own (transcendental) noumenal self and (transcendent) noumenal others through these interactions.
Whatever of the thing-in-itself (ipseic or alteric) that does not participate is unknown. What is known is what participates in particular ways in particular interactions.
For your convenience, here is Peirce’s Pragmatic Maxim, because it should be coming to mind: “Consider what effects, that might conceivably have practical bearings, we conceive the object of our conception to have. Then, our conception of these effects is the whole of our conception of the object.”
… Once again, I feel like I’m lurking about in the suburbs of Whitehead. …