kde monitoring tools do not see network

[Andriy Gapon]

Since upgrade to Plasma 6 neither various plasmoids nor System Monitor 
application can see network interfaces / stats.

System Monitor has an error line saying "This page is missing some sensors and 
will not display correctly" and a "Fix..." button.
If I press the button I am presented with a dialog titled Replace Missing 
Sensors with a list of network related items such as "network/(?!all).*/upload".
But I have no idea what to do there.

-- 
Andriy Gapon