It seems to me there are a number of problems with the concept of omniscience.
The most glaring problem is that God has an enemy (how anthropomorphic is that?): the Devil. If God possessed omniscience, this would render any opponent impotent, wouldn’t it?
If God knows everything, he would know every possible way to avoid any attack by the Devil. He would also know every counterattack against and vulnerability of the Devil. Moreover, he would also know every plan the Devil would or could conceive of. Just thinking about how to destroy God would be a fruitless and incriminating task. This doesn’t seem like a fair fight.
So, either God is not omniscient or the Devil doesn’t exist. Or of course, it’s all nonsense.