It appears that instances from geometry nodes aren't getting their IDs properly translated to the Octane scene graph.
I made a test with geometry node instances to the left, and instances on faces to the right. As you can see in the first image, the instance range node isn't working with the geo node instances, but it's fine on the face instances.
I checked the Octane scene node graph, and sure enough, the scatter node corresponding to the geometry node instances has '0' for every ID field.
I have verified that under to Object properties, Octane Settings > Object Type is set to 'Scatter', and 'Maximize Instances' is on.
The Random Color Texture node seems to work fine, which I guess means, that it doesn't use the ID field at all.
One other thing I'd like to clarify,if a developer is around: does Octane make any use of the ID attribute from Geometry Nodes?
Thank you,
Sebastian