OK.. there is a script (which needed a quick update.. available 35 days from now) which will convert scenes including Ultra Scattered instances into objects;
Instances to Objects;
https://www.daz3d.com/instances-to-objectsWillow Creek by stonemason is a serious mess for Octane to handle;
https://www.daz3d.com/willow-creekIdeally the plug in developer would look up the single function call that can to solve this... but if you run this script from Daz it will do the conversion.
However it results in an insanely large number of objects seriously slows Daz.
Turn off 'visible in view pane', and 'selectable in view' for all the converted instances.The Octane plugin is another concern. Do not use the plug in without taking some precautions and being careful. (It renders fine, but using the plug in is an effort.)
Before attempting to even look at or edit textures, make sure only a single texture is selected in materials under Scene Surfaces. Otherwise the plugin will hang forever (I gave up after 5 minutes) when the menu attempts to highlight all the surfaces using that material. There are like 1700 (?) Grass Instances in Willow Creek.
You still have to deal with horrific lists of items when you start to work the textures. Its insane. Be patient and you will get through this.
Save Often, and double check that you only have one material visible under Scene Surfaces.