I think that the RED test footage for ACESnext may be in ACEScg (AP1) rather than in AP0 (spoiler: it is not). This is particularly noticeable in two images when viewed through OpenDRT.
First here is the JPG from the RED website as a reference for how the image should look
Next the EXR from the Dropbox in AP0 color space:
now with AP1
The AP1 looks much closer to the reference, while the AP0 has more red in it, most noticeable on the back wall. This lead me to suspect that the image may have been mistakenly output in AP1 color space, rather than AP0.
As a test/experiment I downloaded the R3D and made a new EXR in AP0 while viewing it through OpenDRT.
Here’s the ref from the RED website:
Next the EXR from the Dropbox in AP0 color space. Note the color of the clouds:
Same in AP1, which again more closely matches the ref:
and once again my experimental EXR from the R3D in AP0 made viewing through OpenDRT:
I was not able to tell visually whether the other RED footage was in ACEScg (AP1) too, but strongly suspect these two images are. Wanted to flag that as I assume they are supposed to be in AP0.