We don't know anything objectively. We may believe that we do but this is a delusion. Everything we know is subjective. There are two kinds of subjective truths:

1. Exclusive subjective truths e.g. your thoughts, your dreams, your hallucinations, your pain, your pleasure, etc. Only you have access to them.

2. Shared subjective truths e.g. things two or more sentient beings can experience e.g. standing on the planet Earth, looking at the stars, eating at a restaurant, flying in a plane, etc.

I'm not sure what your definition of "objective," is here, but it seems like the objective should be a subset of number two. The objective is the view of things with biases removed, accounted for, or flattened out.

Objectivity cannot exist without subjectivity. For a world without any experiencing beings, talk about the "objective existence of things," becomes meaningless. Without the possibility of subjectivity, "objectivity" is a contentless term, seemingly applying equally to everything and nothing. "Objective," just becomes equivalent with "is," the term doesn't delineate any possible distinction.

There is, of course, a tendency to make "objective" a synonym for "without reference to mind," "noumenal," or even "in-itself, relating to nothing else." I don't think this is a helpful redefinition. If anything, it seems like a conflation, and it becomes particularly pernicious if combined with the idea that "objectivity approaches truth at the limit," or "the true view of things is the view from nowhere/anywhere."

Of course, it's true that a knowledge relationship cannot exist "without reference to a knower." But then it hardly seems like "without reference to a knower," should be the gold standard of knowledge. This is the incoherence at the center of positivism, whose ghost lingers on as a sort of voodoo strawman held aloft by post-modern thought as the foil that can be defeated to show all notions of objectivity and truth are relative or empty. But that the idea that "the truth of things is how they are conceived of without a mind," is simply broken doesn't really say much about truth and objectivity as a whole.