Can there be absolute truth without an omniscient creator? My guess is no.
Even if we ignore Deeviant like one ignores rude children, your question still needs a bit of clarification for people to answer.
I'd eliminate the semantic definition of truth right up front because philosophically-speaking at least there isn't anything very deep in that perspective (even if it does help us understand communication). For the same reason we can eliminate the sort of truth that describes “correspondence” between one’s words and the actuality of occurrences in external reality.
I’d have trouble with what you seem to be implying too. It seems by linking absolute truth to omniscience you are suggesting the "truth" has something to do with knowing. In that case, I suppose we'd need an omniscient "something" for an absolute truth to exist. But that is not necessarily the best way to define truth. For example, if something is true about reality, but no one knows it, is it still true? Yes it is. We know this because lots of things have happened in the past which we are just now finding out about, and whether we knew about it or not had no effect on the occurrence. Therefore, it seems to me that truth and knowing the truth are two different things.
So possibly a better definition of truth is to call it that which actually exists or happens; we might also include the potential for something to exist or happen. With that definition we can also say if something does not exist/happen, and cannot exist/happen, then it isn't or can't ever be true (I’m including “happen” because the word “exist” seems static and doesn’t describe the dynamic aspects of reality too well).
Such a definition gives us an avenue for contemplating "absolute" truth. If we look at everything which we know to exist/happen we can see they had a beginning. The universe is believed to be 11-13 billion years old, but before that as far we know it wasn't there. So before it was there, the potential for it to come into existence had to be there first. Similarly, life and consciousness now exist, but at one time they (apparently) didn't. So before they came into existence the potentiality for them to exist/happen had to be there first.
Now, what is that "raw" potentiality like? Is it some “absolute essence”? Is it conscious? Is it “nothing” as some speculate (personally I don’t think that makes sense at all)? Well, whatever it is, we can see it is incredibly versatile because of all its manifestations here in our own universe.
Getting back to your question, I am suggesting that one way to look at absolute truth is as that raw, unmanifested potentiality which allows everything to exist/happen. In this idea, nothing can be except what absolute potentiality can become. Because we see in our own universe order and limitations, “absolute” doesn’t mean that potentiality can become just anything; apparently to manifest it has to follow rules. Absoluteness, then, is determined by the possibilities and limitations of absolute potentiality. With such a definition we have a means for talking about what is true (i.e., does it or can it exist/happen). We say is it “true” that God exists? Is it “true” that the brain creates consciousness? Is it “true” that the universe began with the Big Bang? Is it “true” that time travel can happen?
(To add a practical note, if we understood what absolute potentiality was really like, we could also say more about the nature of what now exists. Right now everything we say is relative to other things, all of which are manifested potentials of the absolute. We cannot compare “things” to the absolute [because we don’t understand it], and I believe that prevents us from seeing the common thread that runs through all of existence. As a result, none of our models of "things" include the absolute aspect; but if it did, possibly we'd have a deeper understanding of reality.)