I'm new to Linux, and KDE in particular.

Backstory:

I've upgraded from Kubuntu 18.04 to Kubuntu 20.04 recently, and I've encountered a weird problem when I try to install a new theme.

I install themes using the "Global Theme" menu in the settings, by clicking the "Get New Global Themes..." button. The theme I choose, is being installed correctly, but, when I press the "uninstall button", and it disappears from the "Get New Global Themes" browser, I can still see it in the menu of the Installed Global Themes, alongside with the default themes that came out-of-the-box with the system.

And of course, the files of that "deleted" theme are still present in the system, even tho, I clicked on the "uninstall" button. (reboots don't help)

I didn't have that problem when I've been using Kubuntu 18.04 and it only appeared after the upgrade. I already read this thread, but I would like to ask again, since the answer in that thread isn't clear enough for me.

The question:

Is it a problem on my side? If so, what should I do to fix it, and not delete all the files manually?

If it's a KDE problem, do you know whether it was fixed in the latest KDE Plasma releases? (I.e. Plasma 5.18.5, etc.) -- I could not find any relevant information regarding this topic besides the thread I mentioned above.

Thank you very much in advance.