This was surely one of the nuisances I experienced at first on Plasma.
Because we were accustomed to another workflow on the other desktops. That is all it is. A personal preference.
If you want to able to click a file or folder to be able to select it and delete it for example then you need to change a setting.
The image above and the video below show you what setting needs to be changed.
You can keep the setting to single-click to open files and folders and use also CTRL or SHIFT to select the files or folders with your mouse WITHOUT opening it.
You can follow our tutorials based on either of two iso's.
1. ArcoLinuxB Plasma (recommended)
We record the plasma video's on an SSD installed from the ArcoLinuxB Plasma iso.
You can either create your very own ArcoLinuxB Plasma iso following this tutorial or download it from Sourceforge. (ArcoLinuxB-plasma-18.11.2.iso of 4.3 GB - games included)
2. ArcoLinuxD Plasma
You can also use the ArcoLinuxD iso and then install Plasma with the help of the github scripts. This will not be an exact copy of the iso.
Learn about the Plasma desktop and enjoy it.