"the dead don’t know anything" (9:5), and "there is no work, nor plan, nor knowledge, nor wisdom, in Sheol" (9:10). What is the Preacher saying about the dead?

The chapter gives these words with their reasons, after For or for. "For to him who is joined with all the living there is hope; for a living dog is better than a dead lion" (9:4). "For the living know that they will die, but the dead don’t know anything, neither do they have any more a reward; for their memory is forgotten" (9:5). And of the dead: "neither do they any longer have a portion forever in anything that is done under the sun" (9:6). Then come the Preacher's commands to the living, beginning "Go your way" (9:7), and the last of them gives 9:10's words as its reason, after for: "Whatever your hand finds to do, do it with your might; for there is no work, nor plan, nor knowledge, nor wisdom, in Sheol, where you are going" (9:10) (tap Sheol). The book says more near its end: "and the dust returns to the earth as it was, and the spirit returns to God who gave it" (12:7). And it closes, "Fear God and keep his commandments; for this is the whole duty of man" (12:13), "For God will bring every work into judgment, with every hidden thing, whether it is good, or whether it is evil" (12:14). Chapter 9 says no more about the dead than these verses. These notes build no teaching on what happens after death from them, and don't make 9:5 or 9:10 the book's last word. They let the Preacher's words stand as he says them, beside the book's own close.