I do not think that you need to introduce wave-function collapse here, because there is no need for the universe to be fundamentally non-linear - it suffices fo

I do not think that you need to introduce wave-function collapse here, because there is no need for the universe to be fundamentally non-linear - it suffices for the Poincare recurrence time to be extremely large. Like phase transitions in statistical mechanics, could it no be that chaos is just an emergent effect that arises from the quantum dynamics of infinitely many particles? (The appearance of non-linearities in that limit happens to also be discussed in the MIT paper of the quanta article.)