Does truth exist in hell? is an interesting question, but I believe it starts with a presupposition that something can exist separate from God which is a contradiction to the Nature of God and Creation.
Hell is described in Scripture as a definitive place in creation. Consequently as it is a created place - it was created by God. Being created by God by its very nature of being created it must contain at least in part the Truth of God.
So what is Truth in Hell. The primary Truth of Hell is the fact that it witnesses by its existence the Truth that a Just God exists. Scripture states that ALL will be brought before the Judgement Seat of God. As Mat 25:31-46 says God will divide the sheep from the goats. Consequently many believe, as I do, that for all the suffering that exists in hell, the pinnacle of that suffering is that those there will have full knowledge of the existence of God and His Nature limited only by their capacity to understand as a created being AND that they will exist forever totally separate from God. Some believe that Hell is actually a place where the Fire of God’s Love is forever purifying sin from the being of those that are there.
So my answer would be emphatically YES. Truth does exist in Hell.
Hopefully this is some food for thought.