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 other pragmatic way to interpret this scripture other than that dead souls are entirely unconscious.
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 interpreted as talking about dead bodies/spiritually dead. Sheol is incontrovertibly the place of dead souls; ask any reputable scholar or assess any Hebrew lexicon. The author makes it clear that in Sheol, the place where all dead souls are found, consciousness 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, does not make a reference to life or the living. 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(not plain and easy to swallow/agreeable). To say anything otherwise would be to go beyond what is (so clearly) written(i.e. to add to what is written in 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."
Does Ecclesiastes Support the Sadducees?
Does Ecclesiastes 9:3 deny the resurrection? No.
Ecclesiastes 9:3 "This is an evil among all that hath been done under the sun, that one event is to all, and also the heart of the sons of man is full of evil, and madness is in their heart during their life, and after it -- unto the dead."
Notice this scripture does not state that death is the only event that all people share, but that death that one event that all people share, i.e. that death is, at minimum, the one event that all humans share in participating in.
To illustrate with a simple statement; "The one thing me and my wife will certainly do together on our vacation is to go to Disneyland." Does that statement imply that going to Disneyland is the one and only thing me and my wife will do together on our vacation, and thus excludes the possibility that we share in participating 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. And that does not strictly forbid us from participating in any other events together. Death being one event all humans participate in is not mutually exclusive with the event that all humans are resurrected. To be clear, I am not interpreting V3 idiomatically. I am showing why death being "that one event" that all share(as per Ecclesiastes 9:3) does not have to be interpreted as the one and only event that all share, but can instead be interpreted as the minimum of events that all people share, or simply an event that all humans participate in, with no reference to the happenings(or lack thereof) of any other events(e.g. the resurrection). Thus, Ecclesiastes 9:3 does not oppose the resurrection.
As you can see, Ecclesiastes 9:10 unambiguously and indisputably proves that the dead know naught, and corroborates what is said 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.