When opening a .deb file, if a previous version of the package is already installed, Discover does not offer to update the package but only to remove it.
STEPS TO REPRODUCE
1. Install some package
2. Fetch the .deb of a newer version of the same package
3. Open this .deb with Discover
On right corner, there is only a button to remove the package.
There should be a button to install the new package (= update current version).
Linux/KDE Plasma: Debian 12 (almost stable)
(available in About System)
KDE Plasma Version: 5.27.2-1
KDE Frameworks Version: 5.103.0-1
Qt Version: 5.15.8
More info: if the user clic on the remove button, package is not removed but updated properly. After that, the remove button is still present but clicking on it again has no effect.