Created attachment 139174 [details]
The popup and its setup. The connection-specific sensors work, but the non-specific sensors show 0.

I just upgraded from Plasma 5.21.5 to 5.22.0, hoping it would fix that text-only sensors were not shown in the networkmonitor widget. That was indeed fixed. :)

But now I discovered another problem in the same widget: I have two lines and two text-only sensors for up- and download: the former for the current rates and the latter for the totals. After the plasma update I closed the session and logged back in. Now all those numbers were shown as 0, there was no apparent movement in the line graph.

As a workaround I found that I could replaced the sensors that accumulate over all interfaces/connections with connection-specific ones.

On a sidenote, please observe the layout problems, causing ellipses to appear at different locations in the popup.