The plasma-applet-netspeed widget is no longer available due to KDE updates

Related issue: The widget cannot display the netspeed correctly in new version of plasma · Issue #28 · dfaust/plasma-applet-netspeed-widget · GitHub

Although some people claim that installing libksysguard can solve it, but it doesn’t work on NixOS. Does anyone care about this problem? Although this may be a problem with widgets or KDE itself.

The related topic seems to conclude that ksysguard needs to be installed on the system.