Okay, I did some tests with my UR816C and NO controlroom activated. Then you can use the hardware rack, but only in the Arrange-window. I cannot see it in the cubase mixer anywhere.
What you can do in the mixer however if you want the harwarerack postrecordings, is using the seperate plugins from the UR816C as inserts, they are in the Steinberg folder.
In the arrangewindow you have the hardwarerack on the audiotrack you want to record on, but indeed it is with the used effects in series so no dry signal can be recorded (as far as I can tell).
So as I said before, I never use the UR816C in this way, even if I wanted, because I always use the Controlroom and then the Hardware rack does not function(still weird, but that’s the way it is).
Instead of this I always have the DpsFX mixer open to make all my adjustments, and then you can record the dry signal while listening to all the effects included.
Hope this helps.