Is Hell Eternal?
Yes. And the totality has verses that suggest it is eternal- not warnings- but descriptive statements of people being in hell forever- and then one verse that says maybe it won’t last forever. I think that’s quite clear to show it is eternal for some people and maybe not for some others
Heaven has a explicit promise and a statement that Allah doesn’t break his promise. The hell doesn’t has a promise that is why it is threat. But both has “as Allah wills” exit clause.