Quick clarification: when you state "my first upgrade to OpenWRT", did you mean it was your first time "installing" OpenWRT on this router.... or did you already have OpenWRT on this router and you were "upgrading" the OpenWRT version?
If it was a first-time install of OpenWRT, I had accidentally installed a SnapShot version, which does not include LuCI. I was able to get to LuCI by installing the Full Version. See this post here.