When configuring the network device sensors (e.g., download speed) of a certain device (as widget), the sensor settings are lost on re-login, i.e., no sensors are configured at all.
This might be related to Bug 433951 "plasma systemmonitor network device sensors should actually show the device and not the network", since the actual networks do not exist on login in my case (Networkmanager needs to establish them after providing the credentials via kwallet unlocking).
Operating System: Gentoo Linux
KDE Plasma Version: 5.21.2
KDE Frameworks Version: 5.79.0
Qt Version: 5.15.2
Kernel Version: 5.10.18-gentoo
OS Type: 64-bit
Graphics Platform: X11
Processors: 8 × Intel® Core™ i7-4810MQ CPU @ 2.80GHz
Memory: 15.5 GiB of RAM
Graphics Processor: Mesa DRI Intel® HD Graphics 4600
This is always reproducible when rebooting with disconnected devices. (which is always true for a wifi that needs to wait for a password)
To be more precise, the widget has no more sensors configured.
Furthermore, the widget is in broken state and re-adding the lost sensors to the sensors list does not have any effect. Only removing and re-adding the whole widget solves the issue until the next logout.