No graphics in "CPU History" and "Network History". Just "Memory and Swap History" works. Same as bug 218796, but in 5.9.4 version (previous version worked fine)
Please stay with bug 218796 Also to help it solved you could do as in bug 218796 comment #17 requested
*** This bug has been marked as a duplicate of bug 218796 ***
Solved for me removing ~/.config/ksysguardrc