I recently set up a Raspberry Pi 4 system with Archlinux ARM and Plasma Desktop. With the Raspeberry Pi 4 kernel provided by Archlinux ARM (linux-raspberrypi4 package) the KDE system sensor widgets show no available sensor, while with the stock kernel (linux-aarch64) they work properly. I'm trying to get some help on this, or at least try understand what breaks the system sensors in the RPI kernel but I have no knowledge of kSysGuard et. al so I don't know which kernel features are needed.

Any help is greatly appreciated, thanks in advance.

Did you search for this in the Kernel documentation first to rule out a kernel issue?

FWIW, KSysGuard has been replaced with KDE System Monitor since a while

Which sensors do you want to display? There are like a bazillion possible sensors a computer system can have, and it usually depends on kernel modules to be loaded. This information should be available in the kernel documentation.

Hi, sorry for the kSysGuard - SystemSettings mistake, I'm using Plasma 5.23 so I think I'm referring to SystemSettings, in particular to the desktop widgets. I first tried to ask here on KDE forums since I thought that most important was to understand how SystemSettings reads the information; if I asked to the Raspberry Pi kernel forum and someone would ask "which module/sensor is needed by your monitoring applet?" I would not have been able to answer. And kernel documentation is huge, I really don't know where to start in order to understand how SystemSettings interacts with the kernel and thus what's missing in the RPI kernel.

Anyway, I'm interested in displaying CPU load and temperature, and possibly the network traffic. The fact is, when I try to configure the generic "System monitor sensor" widget then no sensor at all is available, while with the "stock" linux-aarch64 kernel they are. I got no useful info from the Archlinux ARM forums, so here I am...

Again, I might have written this in a confusing way:
All Linux kernel modules have a specific format that will be active and read if it is loaded on kernel start
if a kernel provides the sensor modules then the System Monitor will read it, so the ball is in the camp of the people who provide the specific kernel. Ask them which module has to be loaded to get the sensor inofrmation you are looking for.