If the Universe is infinite, then it is all there is. There is no room for other universes.
It depends on how you define universe.
There are many infinities...and infinity is impossible for the mind to truly understand.
The infinite set of all whole numbers is the same size as the infinite set of even numbers.
1,2,3,4.......
and
2,4,6,8.......
Have the same number of elements....you don’t understand it, you just get used to it....like whacko liberals.(infinite stupidity)