You are right. I use dnf via command-line 99.99% of time but mistakenly clicked update on
the Plasma Updater which might have messed it up.
$ dnf list installed | grep -ie geoclue2
geoclue2.x86_64 2.4.11-1.fc28 @updates
$ sudo dnf downgrade geoclue2.x86_64
Last metadata expiration check: 2:13:30 ago on Friday 12 October 2018 02:31:35 PM IST.
Packages for argument geoclue2.x86_64 available, but not installed.
Error: No packages marked for downgrade.
Why am I not able to downgrade?