HDRI image vs HDRI cube map

The usual ‘gotcha’ is that it MUST be a .hdr
Exactly the same image, at the same resolution, with the same bit depth as a .exr will NOT work
HDRI haven has both, so it’s easy to grab the wrong one.

Also worth noting that 16000x8000px will work just fine. 16384x8192px will hard crash the engine.