I recently ran into a problem when setting up an old computer with KDE Neon for a relative. I don't like using flatpak and snap for several reasons. I won't go into that discussion here, but this computer was a tad old and really needed to conserve storage space, RAM usage and needed apps to load as quick as possible. I also have a custom accessability-focused theme I needed applications to use. So I only wanted to have the regular package system available and not displaying anything from either snap or flatpak in Discover. I thought I could do this simply by removing their sources in Discovers settings, but this didn't seem possible. Clicking the remove icon did nothing and no matter what I did the repos wouldn't go away and apps from both snap and flatpak would be visible when browsing in Discover. Am I doing something wrong or is this a bug? The settings in Discover make it look like they can be removed, but I couldn't get it to work.

I could of course do as I did on my own computer and remove Discover altogether, remove the packages for snap and flatpack and then install Muon instead. But since this computer is for a person who is not very used to computers I thought having Discover for installing software and updates would be more practical.

physically uninstall both flatpak and snap using apt or a package manager (Synaptic or Muon):

You could just uninstall the backends that at Discover uses to work with them ( plasma-discover-backend-flatpak and plasma-discover-backend-snap)
Or to get rid of both systems completely (sudo apt purge flatpak snapd and then sudo apt autoremove). This won't touch Discover at all.

Thanks for your answer! Problem is, when I tried to do that it looked like Discover was about to be removed as well, like it had the plasma-discover-backends as necessary dependencies. Perhaps I should try that again though and double-check.

Lol, I got the package ever so slightly wrong. The package used to be plasma-discover-backend-flatpak, but was renamed some time ago to........ plasma-discover-flatpak-backend. And for Snap it is now called plasma-discover-snap-backend. These should not give you the odd messages, though in the end the correct packages are still removed.

I removed snapd/etc with no issues as well, removing any of these components won't break discover at all, it is all modular.

But if unsure, post the messages and we can look at things from there.

I realized what the problem was: I had Muon set to treat recommended packages as dependencies, and the packages you mentioned above were listed as recommended for Plasma-Discover. With that option off it works fine! Thanks for your help!

As for not being able to remove the sources directly from Discover, I guess that is a bug so if I can reproduce it on another computer I'll file a bug report.