What paragraph 32 doesn’t say is that it is impossible that there should ever come a time where there are no true Cardinals left.
Nor does paragraph 32 state that this document is intended to cover what is to be done in the exceptional event that no Cardinals are available.
In such a case, likely unforeseen clearly by this pontiff, one may need to look elsewhere than this particular document for how to proceed.
On the other hand it is easier to find guidance from the Church on what is to be done if it is manifest that a man is a heretic. Most importantly that such a man cannot be a pope.
But my overarching point was that if you accept that there has been no valid pope since Pius XII, you need to account for how we might choose a new pope, and I've never seen such a plan, based either on scripture or Tradition, from the sedevacantists. The fact that the document governing the election of Pius XII's successor doesn't account for the eventuality that there would be no valid cardinals only argues for his lack of foresight, which I, as a computer programmer, find appalling.
We've had bad popes before, and we can have them again. One problem I see with sedevacantism is that it relies on the teachings of the popes since Pius XII as proof that they can't really be pope. However, the doctrine of the infallibility of the pope is very limited in scope. It must be a matter of faith and morals, the pope (or the bishops in council with him) must clearly invoke the charism of infallibility, and he must be intending to bind the consciences of all generations to believe something that has always been believed by the Church up to that time, though not with the authority he is now invoking. It can't be a new teaching. It can't be a teaching that is now understood in a new sense than it was understood throughout history.
If any of those conditions are missing, it is not proof that the man isn't pope. It is, rather, merely proof that the teaching does not enjoy the gift of infallibility. Not everything a pope declares is infallible. If one can demonstrate how a pope's teaching that clearly seems to have the characteristics of infallibility, yet is clearly heretical, then that would argue for the pope not being a true pope. But even then, one would have to be very careful, because one would have to demonstrate that his interpretation is the only interpretation, and that there is no orthodox interpretation.
Rather than declare on his own authority that such-and-such proves the man claiming to be pope is not actually pope, the more prudent path for the non-theologian in such a situation would be to simply to hold on to what he knows to be true and let history run its course.
I'm not aware any teaching since Pope Pius XII that even comes close to claiming to meet all the criteria of infallibility, even assuming the men who claimed to be pope actually were. Nothing in Vatican II, nothing in the teachings of John XXIII, Paul VI, John Paul I, Benedict XVI, or Francis even came close to claiming to be an infallible teaching. The only exception I know of that could arguably be considered to have made that claim is John Paul II's declaration that women cannot be ordained priests, and that teaching is clearly in line with Tradition.
A much surer path to proving there has been no pope since Pius XII is to demonstrate that the election of John XXIII was invalid. And that's a very high bar to clear, since all the witnesses to his election are dead. All the evidence that has been laid out is circumstantial or hearsay, and there is plenty of evidence to the contrary. Further, given the law regarding the secrecy of conclaves, any hearsay is immediately suspect.
This will be my final word on the matter. Even though I do believe there is valid objective evidence that Francis' election was invalid, I am neither a canon lawyer, nor a theologian, so I am taking my own advice and simply holding on to what I know to be true, praying for both this pope (assuming he is pope) and the next one, and letting history take its course. Anything beyond that is in Jesus' hands.