Just downloaded the latest 2021 beta and inside the Octane Plugin Settings > Output > Color space: If I switch from the default "sRGB (PNG Only)" to OCIO the IPR goes completely black when reloaded.
I do have OCIO v1.0.3 installed in my Windows environment and I think 2021 uses OCIO v2 but I'm using the "Automatic intermediate color space" so it should be using the OCIO info that's included in Octane.
The last version of Octane I had installed previously - 2020.2.5.0 - worked correctly.
A. Windows 10
B. 2x 2080ti
C. 64gb
D. Nvidia driver v 471.41
E. OctaneRender Standalone version 2020.2.4
F. OctaneRender plugin version 2021.1.0.3
G. Houdini 18.5.633