I know a few HDRI sites, but I can’t seem to find a single decent HDRI that consists of only a sky and sun (the sort you get in various game engines by default), so is there a place where I can find them?
Not free, but there’s https://blendermarket.com/products/pro-lighting-skies
What about https://hdrihaven.com/ ?
I don’t see any, there’s some that have a bit more of the sky and some a bit less, but they all have ground, I am looking for something that is sky only.
You can just take one from hdrihaven and mask out the sky. Clone a few areas here and there and you got a sky dome.