I just want to warn you that Yubikeys download area seems a bit confussing. But one thinks when checking is that Just need to install release 2.0.0, but that release only has 2 factor authentication plugins. So If you want to use the One factor authentication you need to install also Release 1.0.0 package.
It seems to me after reading releases description that user and authentication plugin are missing from Release 2.0.0:
https://www.akeebabackup.com/download/yubikey.html
Best!!