So “3D grid only in the [0,1] range and use N=32.” aside ( why do so many threads feel like a maths exam) 
So does in fact the VFB export luts correctly? 
Not just that…because it may technically be correct…Id ask, What needs to be done to ensure a LUT from the VFB works correctly in Photoshop?
So from how I understood it, it only works as expected as long as you don’t have intensities higher than 1.
In other cases you will get wrong results and there is not really a way to transfer the adjustments in the VFB 1:1 to Photoshop (or any other software).
That’s a bit of a bitter pill to swallow, hope there can be a solution for this. The trick with the channel mixer is great, but I think 99,9% of users are not aware of this and will wonder why their picture in PS looks wrong…
exclude tone mapping step from lut and do it separately. adjustment layers, ocio plugin - whatever works for you.
I settled on Reinhard+curves as it’s available in almost all possible post production apps and was a standard for years with VRay.
practicality of using luts for tone mapping was discussed on aces forums a lot.
funny story about those 99% - I tried sharing two yt videos about correct hdr compositing in Photoshop on two biggest VRay groups on Facebook as I heard “socials” are the place now for industry chitchat. both were blocked by moderators.
Thats unfortunate, but if you accept my 2 cents: In order to be succesful on Social Media your videos would need to be prepared in a slightly more “watchable” way. I think the content is great and it helped me with my issue, but if you wouldn’t have specifically pointed me to that video I don’t think I would have ever clicked it. I think the problem is more in the presentation than the lack of interest by users.
heh, good point. not interested in reaching bigger audience though. too old for that game and this is the production value I can afford really. but I do enjoy sharing as this is how I learned ages ago. and if even two people find it usefull - I’m good and happy. on the line are even more obscure topics like colored film grain “in camera” in VRay and rule of thirds composition being a cancer on modern photography. not a vast audience for those but I will be delighted to deliver both.
going back to Photoshop used for hdr postproduction - my first quick tip is always: use Affinity.
Sounds awesome, I subscribed and I will surely check this stuff out 