The new system monitor in KDE Plasma, "plasma-system-monitor", while looking better, is lacking some features from the older one, ksysguard.
1. In process list, some columns are missing, like CGroup.
2. Change processes' priority (renice) in process list.

However these can still be accessed in another application, the "systemmonitor" without the "plasma-" prefix. It can't be found in app launcher, but has a keybind (defaults to ctrl+esc). it will be better if "systemmonitor" can be integrated into "plasma-system-monitor", at least a shortcut in the tools list.

Also, operations that need password for root permission, like increasing priority or killing other user's processes, still needs a daemon from sysguard to be installed and running. Otherwise, both system monitors simply fail, and the error is logged to console. In Ubuntu 22.04, the required package is "libkf5sysguard-bin".