Lenovo y550 (gt m240) vs Ubuntu 17.07, 16.04, 14.04

Unfortunately, nothing obvious in acpi. So we need more info. Since nouveau seems to work, let’s see where that gets its vbios from. Switch to nouveau and add the following to kernel commandline

nouveau.debug=debug,VBIOS=trace

Reboot, run dmesg > dmesg.txt and attach.

While you’re running nouveau also extract the vbios to a file:

cat /sys/kernel/debug/dri/0/vbios.rom > vbios.rom

If not found, look if there is more than one directory in /sys/kernel/debug/dri

If no fix can be found there’s always the chance for a workaround, prepare/compile this:

especially those two:
nvagetbios
nvafakebios

Maybe you can use nvafakebios to throw the vbios at the nvidia driver later.