The problem is not necessarily the fire, it is the ‘burning’. I cannot see anything burning outside space and time in the sense we understand what ‘burning’ is. Those in hell presumably do not have physical forms (they are not given resurrection bodies for example). It seems farfetched to imagine God giving the dead eternal bodies and creating a physical world with eternal fire for them to suffer in.
I would find the idea of simply suffering beyond our human comprehension outside time and space to be a more likely truth when it comes to the reality of hell, and it was written as burning to communicate the highest form of suffering to the Ancient Jews of this period. God could have made a word for this suffering, but it would have been lost on human beings who had no way of experiencing it in their physical reality.
It’s clear that Satan, the antichrist and the false prophet are all thrown into the “lake of fire” and tortured forever, and those whose names are not found in the book of life are thrown into the same place after the Great White Throne judgment.
You’re correct that it might be some sort of unknown torture, but the “rich man” in Luke 16 was wanting Lazarus to bring a drop of water to cool his tongue from the “phlox” (flame) he was experiencing. So it felt like torturous flames to him.
Also, the dead “stand before,” “histemi enopion,” God.
Rev 20:10 And the devil that deceived them was cast into the lake of fire and brimstone, where the beast and the false prophet are, and shall be tormented day and night for ever and ever.
Rev 20:11 And I saw a great white throne, and him that sat on it, from whose face the earth and the heaven fled away; and there was found no place for them.
Rev 20:12 And I saw the dead, small and great, stand before God; and the books were opened: and another book was opened, which is the book of life: and the dead were judged out of those things which were written in the books, according to their works.
Rev 20:13 And the sea gave up the dead which were in it; and death and hell delivered up the dead which were in them: and they were judged every man according to their works.
Rev 20:14 And death and hell were cast into the lake of fire. This is the second death.
Rev 20:15 And whosoever was not found written in the book of life was cast into the lake of fire.