I wanted to check in with using a Blender generated environment texture with this process. @PatrickRyan, pointed me to this video, where you can make a panoramic equirectangular image of your Blender scene.
The video is using an old version of Blender, but I found everything in Blender 2.80+, but only if you switch to Cycles from EVEE, which is not a big deal.
The output though is actually a panoramic .PNG file, so I am not sure how coming from that format will work with this?
Getting this process to line up with what looks really easy to make could be a real boon to making some very well lit scenes. I am imagining just putting the camera in a good spot, & adding some Blender lights to a scene I want to export & let Blender generate the file. I can put all the lights & camera in a collection that I can later disable, so that they are not actually contained in the export itself.
Now I am not quite sure that is really going to be what I want. If the lights & camera are all in the right spots though, I could just create another scene of just a large white box on the inside, then file->append all the lights / camera, and take the picture of that.