I don't believe there is a 'beyond' the universe in the sense of there being an infinite void beyond the expansion. I don't believe in voids. I look at it from an 'everything in existence' perspective. Reality is everything in existence and everything in existence is essentially eternal (finite) energy.
The First Law of Thermodynamics (Conservation) states that energy is always conserved, it cannot be created or destroyed. In essence, energy can be converted from one form into another. What that means is reality is not only eternal. it is finite. The words 'infinite' and 'eternal' are often misused. I also sit here and scratch my head when a leading physicist speculates that the universe came from nothing. In order for anything to exist, something had to have always been in existence. That to me is common sense. Perhaps those in the 'something from nothing' camp start with zero in their equations. That might explain it. When you're dealing with everything in existence in an equation, you start with one, not zero. The number '1' represents everything within eternal reality.
It's hard for us to wrap our heads around a reality that had no beginning and will have no end. It's also is hard to imagine there is no 'beyond' reality, which would mean voids are figments of the imagination.
In order for energy to remain in existence, it needs time and space to remain energetic. The way I see it, energy creates its own time and space in ways seemingly too complex for us to grasp. We don't know how many dimensions there are and are just beginning to understand quantum mechanics.
I see the universe as being part of a multi-dimensional reality. In other words, the fabric of our space-time apparently interacts with the fabric of another dimension within the fabric of reality. All of these fabrics are full of energy. Whether there are other universes like ours or one universe connected to all the other dimensions within reality is unknown by us, but not necessarily unknown by vastly superior beings. That would explain all the physics-defying UFO's that are being reported. Vastly superior beings could have been exploring space before we launched our first rocket. They may be able to utilize other dimensions and quantum mechanics to exceed the speed of light and bypass the laws of physics as we know them.