Issue
I'm running Kubuntu 18.04. After installing Steam and Played some games, I found that in System Monitor CPU History & Network history is not showing. I haven't changed any system settings.
How to resolve the issues without unistalling the Steam?
Solution
I got help from another forum. It was a known bug in KDE. Known KDE bug. To solve the issue copy the default “SystemLoad2.sgrd” file from /usr/share/ksysguard/ to ~/.local/share/ksysguard/.
Answered By - Avinash