A number of scientists are of the opinion that the hypothesis of the Multiverse is more philosophical than scientific, since it is not falsifiable, that is, it cannot be refuted using a scientific experiment, and this is an integral part of the scientific method. A separate universe is the universe that does not contact others. And if it does contact, then the group of contact Universes will be one Universe.
Cosmologist Max Tegmark made an assumption, called the hypothesis of the mathematical universe, that any mathematically consistent set of physical laws corresponds to an independent, but really existing universe. Unfortunately, this cannot be proven experimentally. However, we have a many-worlds interpretation of quantum mechanics.
Personally, I think, and maybe not only me, that if suddenly the entropy in our Universe does not change or decreases (after all, entropy always increases in a closed system), then she must go somewhere. Maybe through black holes the devil knows where? To other universes? It remains only to come up with and calculate.
Bottom line: no, because you cannot conduct a scientific experiment, because the Universe is a closed system. Maybe, of course, many Universes are in contact, but then they are one system and this is all that we observe and call our Universe.
There are some interesting things here too.
If we mean that somewhere there is a world (worlds) that do not interact with our Universe, then it is not possible to prove this idea in practice. The most you can count on is an application in the form of a hypothesis to any working theory. Practical proof means an opportunity to put an experiment with this parallel world (worlds) itself, but how do you set it up if interaction between worlds is completely excluded?