It looks like this bug may only affect people with hybrid graphics or multiple GPUs and a BIOS that doesn’t allow the selection of a primary GPU. I’ve got a Dell Inspiron 7567 with an nVidia 1050 Ti, and I get the black screen after booting with the nVidia 390.48 driver, although I can use the nouveau driver in 18.04.
According to the bug report mentioned above, the 390.48 version is supposed to include the fix, but it certainly hasn’t resolved the problem for me. I don’t have a /usr/share/X11/xorg.conf.d/nvidia-drm-outputclass-ubuntu.conf file to edit. I do have a /usr/share/X11/xorg.conf.d/11-nvidia-prime.conf that has the “Primary GPU” “Yes” option in it, but it’s overwritten every time by gpu-manager, so commenting that line out doesn’t help.
Is there something else I could be doing to get the nVidia driver to work now that an updated version of the driver has been released?