So, in summary:
1) Swap Green and Blue channel
2) add gamma of 2.2 (TEMPORARY FIX for wrong gamma output bug!)
3) add brightness of 0.5 (shifts blacks to mid grey)
4) make sure alpha values are between 0.0 and 1.0, possibly due to rounding errors from image operations before (or reelsmart will refuse to do anything)
Many thanks, testing it out, some problems but I will crunch a bit more.
I have one more question, if I may steal your time, while you are here :D
I experience strange Color space shenanigans only with Corona:
I know how to correctly do linear workflow, but EXRs from Corona seem to do a strange contrast increase, that cannot be fixed by shifting gamma. As if black levels were changed. No way of getting it correctly in Photoshop, Custom RGBs + Custom Gammas, preserved, discarded, any way I do, it just slaps on some random bullshit conversion. Also there is no option to kill Color handling. Only way I got it near VFB style in Photoshop is with my own applied RGB offset + gamma foolery, which is obviously wrong.
After effects has the ability to disable all color handling which is genius, this lets me import everything as Gamma 1.0 and apply my own gamma 2.2. Simple stuff.
I already gave up on it, tried it all, Changing Input/Output of 3dsMax gamma with MaxScript, since 2014 it's hidden, saved from different VFBs, all to no avail, if it was rendered in corona, my PC just poops on it, unless AfterEffects disable all Color handling. Did I miss something obvious?
edit: only concerns openExrs