I always thought of our universes as just a bubble, with dark matter all around us. It’s not the edge of the existence as much as the edge of our bubble.
We might not be the only bubble, but it’s impossible to interact or even observe them. Could be millions, could just be us. No way to every know.
Our bubble keeps expanding, until the edges aren’t dense enough to displace whatever’s out there. And we’ll either slowly fade and future civilizations will assume the universe has always shrunk. Because that’s all they’ve ever seen. Like if the human lifespan was a single minute, people would freak out everytime it approaches dawn or dusk. Not understanding that it’s a cycle.