Einstein’s general theory of relativity suggests that our universe is finite but lacking a boundary or outer edge. Huh ? No comment..lol

It's speculated that space is flat, not flat as in 2D, but 3D kinda flat. The same way that the shell of a black hole is theorized to be a flat projection of everything that's in it. That's because when you theoretically shine two laser beams parallell to each other out into infinity, eventually they'll collide. How can two straight parallell lines cross each other? well draw two straight parallell lines on a globe/sphere and you'll see for yourself. But take it with a grain of salt, all of this, since we're stupid human beings that not so long ago thought earth was flat. Including your statement.