Sabine Hossenfelder is against the idea of the multiverse. Michio Kaku is for it.
At the risk of writing another "schizo-post", I wish to emulate some thoughts about this idea - the multiverse. But first, I need to define what I mean by "Universe".
One interpretation of "universe" is the naively realistic view that it is merely the arena of spacetime which we all share. That means including us, the Earth, the Sun and Solar System, the Milky Way galaxy, and all the stars, galaxies, black holes and spacetime beyond, from the beginning of time till now.
But another viewpoint of "universe" is merely the one that it is redolent of everything that exists within our own experience. So, my universe is my body and mind, my thoughts and consciousness, and everything else that exists within it. In a way, my dreams are my universe, too.
So on this latter view the idea that there is a multiverse boils down to the notion that other people, other entities, other beings have their own consciousness.
Nietzsche was the first to purport the idea of eternal recurrence. This is the concept that, say you were happy to live your life as you were, with all the same thoughts and in the same time-zone of existence, you'd be happy to relive your life over and over again in the same body, the same person, with the same thoughts and consciousness each time. You would not have free will - that would be an illusion - but you would be happy.
This Nietzschean view of being is one view of the universe that neglects multiple universes, in many ways. There is here, in a sense, no hope of ever ascertaining the existence of others, for example, your brother or sister, or mother and father, or friends, or acquaintances, or strangers and so on. We will only ever be the one person. This is one view in which there is only one universe, and we can not find evidence of other "universes".
The multiverse, therefore, on this view, is not a matter of finding hidden realities where we may have done things differently - that view is surely false. Things are much more immediate than that: the other realities are the consciousnesses of other beings.
And we have indirect evidence for these realities. That is, we have their physical bodies as primary signs that there is life beyond our own.
But the view I am purporting is only solipsism.
So do you believe that Michio Kaku is correct, or Sabine Hossenfelder? The view by Kaku would lead, eventually to a sort of Quantum Leap situation, in which science could find ways of entering the bodies of other people in time and space, and usurping their consciousness. Sabine says there is no multiverse, and I'm inclined to agree, on this view. But the multiverse in this respect boils down to the sense in which we are a different person from moment to moment. But in the sense that we are the same person from moment to moment, the multiverse is false.
However, to say that there is only one universe is to say that the Nietzschean view of eternal recurrence is correct.
Personally, my view depends on my feelings at the time. Sometimes I may be fully Nietzschean, others I may be a little more forgiving and think sympathetically toward the existence of others - the universe of others.
I think that is all I would like to say about the subject.