The issue came after I installed the amd-gpu driver on my Ubuntu 19.04 with the relative fix since it is available for Ubuntu 18.04.
So after installed the driver, the lock screen of my Ubuntu 19.04 stopped to work. I can't lock the screen with the shortcuts (super+L), or (ctrl+alt+L), or simply click the button on the system panel, or waiting the suspend time.
It doesn't work in any manner.
There is a way to fix this issue ?