I installed Ultramarine Linux on my ApolloLake Chromebook using Submarine, and everything works fine except that I can’t get the USB-C port to connect with external displays, and the backlight on the screen isn’t adjusting.
The backlight adjustment keys are working and the value in /sys/class/backlight/intel_backlight/brightness is changing when they are pressed, but the value of actual_brightness is stuck at 0 and the screen isn’t responding. I tried a bunch of things suggested on the Arch Wiki Backlight page such as adding kernel command-line options and installing packages like brightnessctl, but it didn’t seem to make a difference.
With regards to the external display issues, I’ve installed the chromebook-usbc-fix package but it didn’t help. Data transfer and charging work fine. Not sure where to go from here.
If anyone has any idea what might be happening, I’d really appreciate the help. Thanks for all the work you guys do here.