I have an icon that appeared in my system tray, but I don't know what it is supposed to represent. It's the weird gray cable with the three dots on the left of this picture:
The icon is constantly appearing and disappearing (about once per second), which causes all the other widgets to move all the time.
It looks like an AC cable eventually, but it happens whether the computer is plugged or not.
Any idea?
The gray unplugged cable with three dots icon is possibly related to a USB peripheral device. This device may be turning on and off intermittently.
Look at all the connected perpheral devices, and unplug them one by one to see if the icon stops appearing and disappearing.
Make sure that the USB ports are clean and undamaged. Switch the cable to a different USB port if necessary.
Run sudo dmesg | grep usb to show the kernel logs for USB devices.
If you are using a laptop, check whether the behavior persists when it's connected to a power adapter or when it's running on battery power.
Restart GNOME Shell or the desktop environment by logging out and back in again in case there's a graphical glitch in the current session.
Admittedly this is a guess: do you have a USB3 device with a long cable? USB3 has problems with standard cables over 3 m (almost 10 feet). The error message gave me a port and device number but no additional information.
