I already waited at least 1 week, before marking a commit as good. I guess I
will have to try 2 weeks this time. This is going to take ages.

Are you sure, that b7d91c915290ab0bfbab84a0fb9c9eae57816982 is definitely not
the cause?

Maybe some helpful information regarding the bug:

- It appears noticably more often, when rebooting to Linux after gaming in a
dual-booted Windows.
- When booting, the virtual console disappears, the screen displays black, the
login-manager appears. When the flickering does not appear, the black-sequence
(mode-setting?) takes noticably longer, than when the flickering appears.
- We both have two displays. One connected through HDMI, one through
DisplayPort.
- I have two 2K screens, the Fury X-User has one 4K and one FullHD screen.
- We both have the login-manager SDDM
- For me, when booting the machine (BIOS) - the screen resolution of GRUB is
quite random. Sometimes, it's using the native screen resolution, sometimes it
is using a very reduced resolution. Sometimes, it's only displaying on one of
the two screens, sometimes it's displaying on both. But that wasn't a problem
before linux-4.9.