You can render it, you just loose precision.
To understand what happens you can do 2 things.
One is to set up a random level, move to 300 km from 0,0,0 melt the engine a bit, and re-orient the lights with the engine shortcut.
The gizmo on the lower right will show you what happens.
The other is to look at the works modders are trying to get Bethesda’s starfiled to be any decent.
Withough serting anything up you get to see exactly what happens in gameplay and on rendering of such a situation.
As far as rendering from 0km to 300k away.
Thats not exactly possible due to earth’s curvature. But it is in Unreal… a flat earther’s wet dream…
Its just that the mountain range, building, whatever way out there will look like a messy smudge with a vertex every half a hour.
Double precision would make it look like a smudge with a vertex every 30m instead…