How are they real, without succumbing to substance based or essence based thinking? The atta the Buddha was critiquing is a substance. It is something which has an independent existence, meaning ontologically real. Its not a product of the conceptualising mind, according to those who propose it. It really exists objectively. Notice what is happening here?
If dukkha wasn’t real, as experience, why did the Buddha seek liberation from it and teach the N8FP?
Before he was awakened he was unawakened, no? Why does he teach others? Because conventionally there are beings who suffer. Ultimately, there are no beings who suffer because there is emptiness of beings and dhammas.
“Reverends, I have heard and learned this in the presence of the Buddha: ‘Someone who sees suffering also sees the origin of suffering, the cessation of suffering, and the practice that leads to the cessation of suffering. Someone who sees the origin of suffering also sees suffering, the cessation of suffering, and the practice that leads to the cessation of suffering. Someone who sees the cessation of suffering also sees suffering, the origin of suffering, and the practice that leads to the cessation of suffering. Someone who sees the practice that leads to the cessation of suffering also sees suffering, the origin of suffering, and the cessation of suffering.’”
SN 56.30
To see dukkha is to also see nibbāna, which is an emptiness of dukkha. Dukkha includes the earth element, consciousness element and so on. So, by seeing the arising and ceasing of dhammas (1st and 2nd truth) one sees the emptiness of arising and ceasing of dhammas (3rd truth). Its the same thing, looked at from different points of view. Nibbāna is right here, right now, because dhammas are ultimately unoriginated, not found, void. Yet we know the emptiness of dhammas by experiencing dhammas, and so life is like an illusion or a dream. You can’t say an illusion totally doesn’t exist (natthitā) nor that it actually exists (atthitā). This is why its a mistake to say that final nibbāna really is something, or is absolutely nothing.