I reported this on the Linux bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199799
drm/i915 bugreports go to Freedesktop, but Jani Nikula suggested to add "video=VGA-1:e" to the kernel commandline, which fixed this for me. Not sure if this closes the matter, as it used to work without setting video before, but I thought I'd pass this suggestion on to other affected people.
