OK. I guess I figured it out. I installed dnf copr enable mkyral/plasma-unstable and I ran
dnf upgrade --enablerepo=updates-testing --advisory FEDORA-2018-20611f7cb1, but that did
nothing, so I dropped --advisory... and it is presently downloading.
Are there other kde repos from the sig that I need to know about to keep on top of
what's happening?