Comment 8 for bug 1861521

To provide further verification, I built Ubuntu-5.4-5.4.0-14.17 with a single patch on top that reverts commit 3269788061d2 ("USUNTU: SAUCE: drm/i915: Force DPCD backlight mode on Dell Precision 4K sku"). My screen brightness controls are working again and I can undock from my external monitor without having to forcibly reboot the system due to a blank screen on my built-in monitor (I guess my screen brightness is turned all the way down when I undock and I cannot adjust it).