Comment 6 for bug 1742602

I have just had the same issue.

Blank and frozen screen after booting in to 4.13.26 for the first time.
The ubuntu colours are visible and the 16.04 logo also appears bottom left.
The desktop was previously configured to run in 1920x1080. However, the screen changes to 4:3 ratio. No mouse or keys so unable to confirm the actual resolution. I assume it is a default.
I followed another report before finding this one so deleted the .config directory. Ubuntu booted up to a desktop in default resolution. However, the screen then locked when changing the resolution.
Ubuntu 16.04 desktop running inside KVM. So no special graphics installed to speak of. The image is encrypted with LVM inside the qcow file. Requires a password to boot after the grub menu.
KVM hypervisor still running 4.10. Took a deep breath, rebooted and brought the hypervisor up on 4.13. Still the same issues.
ssh on to the desktop machine continues to work fine even when the graphics are blank and frozen.
Followed the workaround above, booted in to 4.10 via grub and everything springs back to life as expected. Able to put the desktop back to 1920x1080. Further reboots into 4.10 maintain that resolution.