>>> Interesting, you should have
>>> /usr/lib/xorg/modules/drivers/modesetting_drv.so shipped by
>>> xserver-xorg-core which would be used on Skylake... can you verify it's
>>> there?
>>
>> Yes, the file exists.
>
> Right, but you also have an xorg.conf somewhere? Try removing at least
> the device section from it.
I never created any xorg.conf file. I installed debian and then didn't change anything in the X configuration.