OTOY has released OctaneRender 4.0 after a long beta period. The update is free for existing customers and new customers pay the same as usual or can try the new rental license instead. The Carrara plug-in was updated along with all other plugins, 14 in total and there is also a purchase option that includes multiple plug-ins.
The list of updates is very long, so head over to OTOY to check out all the new features.
OR 4.0 features: https://home.otoy.com/octanerender-4/
Carrara plugin forum: https://render.otoy.com/forum/viewforum.php?f=79