Most references to death in the OT suggest it man's final state:
2 Sam 14:14 Like water spilled on the ground, which cannot be recovered, so we must die.
Job 7:7-9 Remember that my life is a breath My eye will not again see good…A cloud dissolves and it is gone;
So is one who descends to Sheol. He will not ascend.
However YHWH can restore life if he chooses to: Deut 32:39 "I kill, and I make alive;". Elijh revives a dead child (1 kings 17:17-24) and Eisha does the same (2 kings 4:18-37). But those are revivifications, not indictions that immortal souls are judged and go to heaven or hell. It is worth noting other Middle eastern gods had the power of revivifiction:
And all quarters extolled [his] greatness:.
Who but Marduk restores his dead to life?
Apart from Ṣarpanitum which goddess grants life?
Marduk can restore to life from the grave,
Ṣarpanitum knows how to save from destruction, (trans. by W.G. Lambert, Babylonian Wisdom Literature 1960)
The writer of Ecclesistes has this to say of death: "19 Surely the fate of human beings is like that of the animals; the same fate awaits them both: As one dies, so dies the other. All have the same breath; humans have no advantage over animals. Everything is meaningless. 20 All go to the same place; all come from dust, and to dust all return."
The psalmist writes: "The dead praise not the LORD, neither any that go down into silence." (Ps 115:17) and "For the grave cannot praise you, death cannot sing your praise; those who go down to the pit cannot hope for your faithfulness." (Ps 38:18).
We get the first hint of judgement of the dead in Daniel (2nd century BCE)
And many of those who sleep in the dusty earth shall awake, some to everlasting life, others to everlasting reproach and contempt. Then the knowledgeable shall shine like the brightness of the sky; those who justified the many, like the stars, forever and ever. Dan 12:2-3.
Matthew tells resurrection was not accepted by Jewish Sadducces upto Jesus time. "On that day some Sadducees (who say there is no resurrection) came to Jesus and questioned Him," (Matt 22:23)
Given the weight of evidence that judaism rejected ressurrection, an ambiguous passage such as isaiah 26:19 cannot be taken as proof that a belief in Christianity-like afterlife is ancient. It almost certainly arose in Judea no later than a century or two BC.
"Your dead shall live, my dead bodies shall arise – awake and sing you who dwell in the earth! – for your dew is as the dew of light, and the earth shall bring to life the shades." (Isaiah 26:19)