I agree with @TabNumlock.
I just installed Plasma 5 on another build of Zorin OS. I figured... maybe all my own bad experiences with it were just bad luck or my inexperience - maybe I just never really gave it a chance and gave up too soon.
I opened Settings... and tried to change my icon set.
It wouldn't change.
Finally, it accepted the new icons... Except that some icons were showing as one set and some were showing as the previously selected set.
I closed all windows and opened settings and tried again...
I selected a new set.
Now, all windows showed a complete mash up of All Three Icon Sets.
Opened Dolphin... and I saw some folders in the first set, some in the second, some in the third.
The toolbar icons were the same way - just a mashup of all three sets.
To top it all off (I have noticed this every single time I have used KDE, Plasma etc), all the icons had a strange ugly rough border on them.
I have seen it on Kubuntu, Zorin, SolydK...
Ok fine. Icons don't work. Whatever.
I press on... I try changing Global Theme, Application Style and so on.
Same thing happens - I end up with windows showing a mixup of elements except that Different Windows Have Differing theme elements from the Other windows.
This is not the first time I have experienced this. I just thought may be they were my mistakes or that it was the build or bugs that have since been fixed... I mean, the default theme looked fine. Default Icons looked fine. Until I tried changing them.
And the settings made no sense. They were not logically organized at all. It was stuff thrown all over the place.
I Have Never Seen Anything So Hopelessly Broken.
Sure, I speak in support of KDE and Plasma - but I really only do because it offers an alternative that is Not Beholden to GTK and what Gnome is destroying with it.
But I have experienced Plasma more times than I can count and every single time I try giving it yet another fair chance... I always end up enraged and regretting it.
The (claimed) definition of insanity is trying the same thing over and over expecting different results.
And KDE Plasma is pure insanity.
And the most disgusting of it is... Everytime I load up Plasma I feel just like I am on Windows. It has settings that Windows OS doesn't - sure... But they are so haphazard, broken and strewn around worse than the Windows Registry is.
Windows fills me with Less Rage than trying to make heads or tails of Plasma does.
If I cannot manage Plasma Desktop; it's got issues.
No, it's not me. I didn't give up too soon. I gave up too late - I should have given up on plasma before I typed
y in the terminal to try it out.
And now... I need to go back into that build and try to scrub out the infesting VIRUS that Plasma Desktop is... I will face that later when my blood stops boiling.