https://cosmosmagazine.com/physics/...

Great, but I'm still bothered a bit about how the galaxies are forming "Hello World!".

Well this is assuming that the reality where a computer is simulating us looks like our world.

The article is saying that in order to run a simulation of our world, you would need a computer consisting of more atoms than there are in the universe. Are they forgetting that this theoretical computer is not actually in our universe? That would be a paradox!

They also seem to assume this computer works like our computers do. Which doesn't have to be the case.

It's pretty obvious that you wouldn't be able to run a simulation of our universe inside our universe. However, no one can say if it would be possible in a bigger and possibly more complex universe.