This may be partially redundant with what already written in previous reply:
discovery is a strict requirement of the KDE Plasma desktop environment as it is provided by openmamba so it is by design a requirement of the desktop-base-kde meta package. kwin-x11 is a weak requirement of desktop-base-kde and it is removed because it was installed by desktop-base-kde itself which you are removing, so dnf considers it a leaf which is no longer required. Supported openmamba Plasma desktop users are not expected to remove neither desktop-base-kde nor discover.

By wanting to uninstall discovery you are customizing your desktop installation in a way which is not supported by openmamba, so you will also get desktop-base-kde and, e.g., mambatray tools removed. You can do it but then you have to manage the desktop requirements on your own. You can of course just reinstall kwin-x11 after the removal of desktop-base-kde for your needs. You can also make and maintain your own desktop-base-mycustomkde metapackage if you want and know how to do it.

discovery is a strict requirement of the KDE Plasma desktop environment as it is provided by openmamba so it is by design a requirement of the desktop-base-kde meta package.

This is what I wanted clarity on.
On other distributions I've used previously, discovery is not a strict requirement for plasma.
If this is how it is for openmamba then it is how it is, despite how unnecessary it may seem to me.