To reproduce, launch Discover, and install some app. This will work, but no indication will be given, and the app will still be shown with an 'Install' button. Clicking on it will tell you it's already installed. Similarly, removing an installed app works, but the app remains visible with a 'Remove' button.
Have the same issue.
Still valid in F28 RC-1.1.
I can reproduce too :( What *does* work as expect, if you click on the app to get it's full description... then install/remove there.
same issue, after package install discover not upgrade UI and propose install button instead of remove button
This should be reported upstream (I'll do so as time allows, but if someone beats me to it, they'd be my hero)
Reported upstream https://bugs.kde.org/show_bug.cgi?id=394388
Thank you! will continue monitoring there