nomodeset problem in Jessie, but fixed in Fedora

[Luke <luke@keyee.xyz>]

Hi,
Unless I add "nomodeset" to the grub (specifically:
GRUB_CMDLINE_LINUX_DEFAULT="quiet nomodeset") my pc does not boot (black
screen).
As a consequence, it is not possible to change screen resolution, to use
an external monitor, or to change the brightness.

I checked however that everything works fine with Fedora 24: I guess
therefore that the solution must be in the open domain by now. Just, I
can't find it.

I am running Jessie 8.5 (with kernel 4.6.0-0.bpo.1-amd64)
on a Thinkpad X1 4th generation. More details can be found here: 
https://wiki.debian.org/InstallingDebianOn/Thinkpad/X1%20Carbon%204thGen
%20PCIe_SSD/jessie (I wrote that page).

Any suggestions?
Many thanks in advance, Luke