18.04: USB and other removable devices are not recognized after upgrade from 17.10

I've upgraded from 17.10 recently and now no removable device is recognized.

Neither cat /proc/partition nor fdisk -l shows the devices.

I had the same problem after upgrading 16.04 to 18.04. USB memory sticks, printer or even mouse would not be recognized. As mentioned in the above answer, after 10-20 minutes a memory stick was sometimes recognized. What worked consistently was connecting the device at boot time. Another thing I found was the device WAS listed in the connected devices list but NOT mounted! I could manually mount it with mount command but the mounted device still would not show up in Nautilus!

Finally found the answer when I decided to tackle the laptop overheating problem. (Read about it here: Ubuntu 18.04 systemd-udevd uses high CPU, conflict with wifi). Indeed my CPU usage was at 100%. The moment I disabled bluetooth from BIOS, the CPU usage became normal - between 10 to 25%, overheating stopped and now the USB devices are getting recognized too!

So it means the whole problem was due to high CPU usage! Probably the other processes were not getting CPU time to do their stuff. I'm no expert on OSs, but this is a logical guess :-).

From the comment by Anahit Vardanian:

fixed after changing from X.Org X server to NVIDIA drivers