The client portion of the client/server application sysmon3/sysmond.
This is a follow on to sysmon-qt. A server using sysmond allows multiple workstations to monitor system resoures. A workstation, in turn, can monitor multiple hosts using multiple instances of sysmon3.
There are several ways to monitor the system performace on a Linux system. This includes console based applications like top, htop, free, df, and ps.
For graphical applications there are desktop based programs including gnome-system-monitor, qps (from LXQt), and plasma-systemmonitor.
The problem with the above programs is that they take up a lot of screen real estate. A grapical program that can run continuously but can be configured to use a small amount of screen space is GKrellM. See http://gkrellm.srcbox.net/
GKrellM is a powerful application, but it no longer seems to be maintained. It is gtk2 based and that has reached its end-of-life. There have been no substantial changes to the program since 2016.
sysmon-qt is a program similar to GKrellM but based on Qt6. It does not have all the capabilities of GKrellM, but provides the capability of monitoring CPU usage, memory use, and system temperatures. It is also highly configurable with the ability choose which items to monitor and what colors and fonts to use.