there's a similar question for ubuntu 19.04
I have ubuntu 18.04 since a year installed on laptop Lenovo E590. I didn't have this problem until last 2 weeks (actually between 10 and 18 of March I was using only the built-in keyboard). I suspect that some recent update is the root cause of the issue. How is the 19.04 correlated with 18.04, are some kernel updates backported to the latter with some delay?
$ uname -a Linux WKS 5.3.0-42-generic #34~18.04.1-Ubuntu SMP Fri Feb 28 13:42:26 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux