Fedora 26 is having problems with these. I'm getting things that fail to download from the store. Sometimes things download from the store that aren't recognized as valid packages. Even worse, I have one icon pack that technically installed, but when I look at the log it's complaining it can't remove a lock file that doesn't exist. I can select it, but it doesn't run.

Also the store.kde.org doesn't appear to filter properly for KDE5 compatability, independently of whether it's an icon set, theme, etc. So, it's better to search through google than through the store. I was having similar problems on Mint 18.2. I suspect general broken-ness.

What I would like to know is, what are themes, icons, styles actually. It looks like I should be able to unpack the archive and manually install. However, I'm not sure what the rules are. Can anyone point me to documentation? How hard are these things to make for KDE5? What rules & tools?