although the default user has no password, it is impossible to get out of the lock screen which automatically appears after the display is switched off. Pressing enter on the lock screen with a blank password does not work.
I went to the Ubuntu Studio launchpad site and was told that bugs could not be filed. Therefore, I added a comment to an existing bug filed with Lubuntu for a similar issue (https://bugs.launchpad.net/ubuntu/+source/casper/+bug/2000787/comments/20), but the desktop environments are different. I believe that it is highly inappropriate that bugs cannot be filed and this lock screen problem renders the computer unusable as the screensaver automatically locks the computer if I forget to shake the mouse or to change the power settings.