The people who are having a problem like HDRI backdrop becoming black because of lighting or sky isn’t visible and not working in packaged builds here is a simple solution open HDRI_Backdrop blueprint and change the Mesh variable to EditorSkySphere. This will resolve your problem.
You’re a god!!! Thank you so much for posting the fix. I was starting to go insane 
Build UE5.4.4
It doesn’t work. This is not the solution. It just places the EditorSkydome mesh with default grid tex.
Only way to get it to work my needs quickly, copy the Plugins/HDRIBackdrop materials and rebuild it. Modify attr in the mtl instance to your needs, bp functions are no longer linked.
