Is dukkha conventional or ultimate? Is it different from the other two marks of existence?

Is the existence of dukkha a conventional or ultimate truth? I am confused, because on the one hand, it is usually mentioned together with two other marks of existence, which clearly look like the ultimate truth: "self" is conventional, and ultimately there is no self, and permanence of phenomena is conventional too, and ultimately everything is impermanent. On the other hand, dukkha looks like something conventional: suffering, or lack of satisfaction, depends only on the existence of the sufferer, and ultimately, there is no sufferer, there are only empty aggregates. Moreover, if I were the last sentient being to become enlightened, there would still be no self, and phenomena would still be impermanent. But there would be no suffering. I don't know how to wrap my mind around this asymmetry.