Tintin is becoming Public Domain, but how much?

So, as we all know, Tintin is becoming Public Domain in 2025, but how much. I know his journey to the land of the Soviets was serialized between 1929 and 1930, making approximately half of the story Public Domain next year. But where exactly is the cut off? In current releases, it seems everything is marketed at one volume that at least with what I've found, I have no way of telling which parts of the story were published in 1929 and which were published in 1930.