Kernel 5.9 broke display backlight

It seems that kernel 5.9 (currently 5.9.11-3) introduced a bug that makes display brightness adjustment not work on my Dell XPS 15 9575.

Pressing the keys, the brightness slider moves, but the backlight level does not change - with the exception of 0% turns it off anything >0 returns it to the setting it booted at (50.1…%).
After resuming from sleep, it gets stuck at 1% (very dim).

This problem is not present when booting with the 5.8 kernel. (5.8.18-1)

/sys/class/backlight = intel_backlight
Display driver = video-linux (HD Graphics 630)

see this

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I am happy to tell you, @AJ1, that this screen brightness WORKS on kernel 5.10.7.-3. Hooray!
I also have XPS 15 2-in-1 9575.

Do you think we can update ArchLinux wiki, that it works now? And add that touchscreen is also functioning.