I've updated my kernel from 4.18.16 to 4.19.1 but now the screen resolution is fixed to 1024x768 and Graphics in Settings>Details>About says I'm using llvmpipe (LLVM 6.0, 256 bits).
Also I've listed the modules loaded but there isn't nvidia driver.
How can I repair this issue? I've seen that also with kernel 4.19 other users had reported this issue.
Update: I've upgraded my distro to 18.10 and now if I remove the nvidia driver the system start and use the correct resolution (1920x1080). If I install the driver the system won't start and block at some point of the initialization such as Start Network Manager ecc and not reach login page.
I had the same problem (but could boot with resolution 1024x768, nvidia was simply not loaded) dependig on the nvidia driver for my Geforce GTX 960 and the current mainline kernel.
The problem is the following: The nvidia driver version 390 (used in Ubuntu 18.10) does not support kernel version >= 4.19.
The solution is, that you must install the current version of the driver. The easiest solution for me was to install the package from the graphic driver team:
After that I had Full HD again, using the current nvidia driver. The caveat is, that you must check yourself for new driver versions.