As per the title, the new GUI of Discover has several areas which do nothing more than wasting screen space and lacks proper feedback while performing tasks.

E.g. when searching for updates, a simple progress bar would go a long way to tell the user what's going on.
Similarly while fetching them, we get multiple small progress bars for the different items, but it would be convenient to have one showing the overall progress as well.

"Check for updates" seems to be hidden in the settings menu, which, frankly, does not merit that name at all - it's a confusingly done list of the software sources. Where are the actual settings? Like e.g. settings related to update intervals? A list of sources that's readable for people with less experience in the structure of the repository system?

Searching for updates via apt-get update makes the task-bar symbol show that updates are available, yet to actually show them in Discover, Discover still needs to search on it's own, which can be a bit confusing owning to the missing progress bar.
Sorry if this sounds overly negative, but the basic software/update management app has, in my opinion, always been a weak spot in KDE5 and it does seem to me as if it will stay that way for some time yet.