I wonder if you’re not able to see it in Fortnite because of the Fog. (I was looking at Fog in Island Settings yesterday, and even at 0% it’s still there.)
Without being able to override the fog, I’m not sure having a distant ring would ever work.
I just looked on noclip.website and they have Halo 1 on there! (Scroll down to the ‘Experimental’ section)
You can see that they accomplished the Ring-World with a Giant 2D ‘Card’ or by having it as a part of the sky sphere texture.