Yes, it unequivocally does. Sheol is not the place of dead, rotting, physical bodies, nor is it the place of the spiritually dead. It's the place where the souls of the dead are. There is no pragmatic interpretation of this scripture other than the one that says that the dead are entirely unconscious.
Is Everything Vanity?
Ecclesiastes falls under the genre of wisdom literature, a genre of literature common in the ancient Near East. It's one of three wisdom books in the Bible, the other two being Proverbs and Job.
It opens by telling us that these are the words of qoheleth(קֹהֶ֫לֶת, which just means a collector of words/sayings who speaks them in public), the Son of David, king in Jerusalem. There are many theories as to whom the identity of this qoheleth is(many saying it is king Solomon), but the identity is not vital to our discussion. It then tells us the words of the congregation;
Ecclesiastes 1:2 "Vanity of vanities, says the Preacher, vanity of vanities! All is vanity."
The English translation "vanity" is an unfortunate one, to say the least, especially considering that the author uses it over 40 times in the book. It indicates to readers that what the author is saying is that everything is pointless and meaningless; this couldn't be farther from the truth. The word used there for "vanity" is hevel(הֶ֫בֶל), and it does not primarily convey meaninglessness. Its primary meaning is smoke, vapor, or breath. So, what does smoke have to do with life? Well, like a smoke, life is beautiful and mysterious; it takes one shape, and before you know it, it takes a new shape. And smoke even looks solid, but try to grab it, it slips right through your fingers! It's the same with life at times. You think everything is handled, that you're the one in control, and when you least expect it, life slips out of the grasp of your hands because you can't control where it goes. And when you're stuck in the thick of vapor, like in a fog, it's difficult to see clearly. It's the same when you're burdened by life's problems when it's just so hard to see through the thick fog to find meaning.
Modern translations have lost the metaphor by translating הֶ֫בֶל as meaningless, but the Ecclesiastes isn't saying that life has no meaning; rather, that the meaning of life is never clear! Like smoke, life is confusing, disorienting, and uncontrollable. The book is by no means telling you that the things you do have no meaning or purpose, but that you can never know for sure where they're going to lead you. It's not saying that the reality of the world is that it's worthless, just that the worth is so confusing and difficult to find and get a hold of; it's not that life actually is pointless, but that it's unpredictable and uncontrollable nature can leave you feeling like it's pointless. This is a fact of life that no one can argue with. This book is not an atheist's book; it's an every human on earth book. If you tell me that you've never felt like life is meaningless before, then I know you are lying, because every human who has ever lived has. That is the mere fact that the book is trying to convey. So, when you see "meaningless" in your translations, don't think that the book is telling you that life is, in reality, meaningless, because that would go against the rest of what the Bible says; rather, think that it's telling you that life is unclear and unpredictable, such that at times it can leave you believing that there's no point to anything. This does not go against anything that the Bible says. It's recorded in the Bible that Elijah, a righteous prophet, had suicidal thoughts(1 Kings 19:4)! If that man didn't thoroughly believe that life was pointless at that moment, then no one does! So, no, Ecclesiastes does not go against the Bible when it says that life is הֶ֫בֶל.
Is There Any Other Way?
Ecclesiastes 9:5 is a little more ambiguous than 9:10;
"For the living know that they will die, but the dead know nothing. They have no further reward, because the memory of them is forgotten."
Does the author mean the spiritually dead? Does he mean dead, physical bodies? Many have tried to interpret it as such. Ecclesiastes 9:10, however, cannot under any circumstances be taken to be talking about dead bodies/spiritually dead. Why? Because Sheol is incontrovertibly the place of dead souls; ask any reputable scholar or assess any Hebrew concordance. The author makes it clear that in Sheol, the place where all dead souls belong, knowledge/thinking ability/wisdom/work is possessed by no one.
Also, notice how the scripture does not say the dead in Sheol have no knowledge of what is occurring apropos the living/life. The passage does not say that there is no knowledge being acquired about the earth and its happenings in Sheol. What it says is;
Ecclesiastes 9:10 "Whatever your hand finds to do, do it with your might, for there is no work or thought or knowledge or wisdom in Sheol, to which you are going."
As you can see, it does not make a reference to life, the living, the earth, or anything of the such when it comments on knowledge, wisdom, etc. The only location in question is Sheol.
It straightforwardly says what it says; that those in a state of death in Sheol have no work, no device/thinking ability, no knowledge, and no wisdom, end of story; plain and uncomplicated(I didn't say plain and easy-to-swallow/agreeable). To say anything otherwise would be to go beyond what is written(i.e. to add to scripture what clearly isn't found), which we are warned against by the apostle Paul at 1 Corinthians 4:6;
1 Corinthians 4:6 "I have applied all these things to myself and Apollos for your benefit, brothers, that you may learn by us not to go beyond what is written, that none of you may be puffed up in favor of one against another."
Paul's words seem like a precursor to Occam's razor, don't you agree? While we could posit that the correct interpretation of "there is no knowledge in Sheol" is actually "there is no knowledge of the happenings of the earth or of those living on it in Sheol", it is orders of magnitude more reasonable to simply interpret "there is no knowledge in Sheol" as "there is no knowledge in Sheol", and anything more than that when unwarranted by the text itself(i.e. there is nothing in the text to suggest otherwise) is not only unnecessary, but makes for a hermeneutically flawed interpretation.
Notwithstanding that if you interpreted "knowledge" as "knowing about what goes on in earthly life", so as to stay consistent within the immediate context of Ecclesiastes 9:5, you'd have to say the same about "device", "wisdom", and "work". Do the dead not have wisdom about what happens on the earth? Do they not have device about what happens on the earth? Do the dead have work about what happens on the earth? That's all pretty much nonsense... You could, of course, always say that the author is informing us that the dead have no wisdom, device, or work period, but then you'd be forced to say the same about knowledge, no? You don't get to pick and choose which is talking about which and blow the context to hell(no pun intended). Either the entire passage is with regards to earthly happenings, or it's not.
Does Ecclesiastes Support the Sadducees?
Does Ecclesiastes 9:2-3 deny the resurrection? No.
Ecclesiastes 9:2-3 "All things come alike to all: there is one event to the righteous and to the wicked; to the good and to the clean and to the unclean; to him that sacrificeth and to him that sacrificeth not; as is the good, so is the sinner; and he that sweareth, as he that feareth an oath. This is an evil in all that is done under the sun, that there is one event unto all: yea also, the heart of the sons of men is full of evil, and madness is in their heart while they live, and after that they go to the dead."
Notice this scripture does not state that death is the one and only event that all people share, but that death is one event that all people share, i.e. that death is the minimum event that all humans share in participating in.
To illustrate with a simple statement; "I and my wife going to Disneyland is the one thing we will certainly do together." Does that statement imply that going to Disneyland is the one and only thing me and my wife will do together on our vacation, thus excluding the possibility that we share in any other events? It's possible to interpret it that way, but you could also interpret it to mean that the event of me and my wife going to Disneyland together is the minimum of events we will participate in together. Such an interpretation does not forbid us from participating in any other events together.
Death being one event all humans participate in is not mutually exclusive with the event of all humans being resurrected. To be clear, I am not interpreting V3 idiomatically. I am showing why Ecclesiastes 9:2-3 saying that death is "one event" that all share does not necessitate that we interpret it as the one and only event that all share(in fact, it seems that interpreting the text in such a manner is more idiomatic than not). It can just as easily be interpreted as the minimum of events that all people share in participating in, or simply one event that all humans participate in, with no reference to the happenings(or lack thereof) of any other events(e.g. the resurrection). That is the plain reading of the scripture. It is not necessary to take it as saying that death is the only possible event all humans share, excluding the resurrection in the process. Thus, Ecclesiastes 9:2-3 does not contradict the resurrection in any manner.
As you can see, Ecclesiastes 9:10 unambiguously and indisputably proves that the dead know naught, neither have they wisdom, thinking ability, or work of any kind, hence corroborating what is told at Ecclesiastes 9:5, Psalm 6:5, Psalm 88:10-12, Psalm 115:17, Psalm 146:4, and Isaiah 38:18-19, bringing everything together in total harmony.