dim screen after kernel upgrade
So it appears there's a problem when upgrading from older kernels to something around 5.5 or later.  The symptom is that when you boot the new kernel, the screen is very dim, possibly appearing completely black.
The problem seems to be that with the older kernels, screen brightness was on a 8-bit 0-to-255 scale, and the newer kernels use a 12-bit 0-to-4095 scale.  So the reasonably bright "224" (for example) brightness that you had with the old kernel becomes a rather dim "224" with the new kernel.

It seems that this issue occurs with a few different distributions' kernel packages.  I'm not sure if any distributions have any fixes (maybe a transition script) built into their kernel packages.

My current thinking is that the best approach (for individual users) is to verify that your Fn-F1 and Fn-F2 are working for adjusting your screen brightness before upgrading the kernel.  Then when you boot your new kernel and you can't read the screen you can use them to turn up the backlight.  I neglected to do this.

A hackish approach could be to poke at the files in /sys/class/backlight/edp-backlight/ (you could do this via SSH if you can't adjust brightness via the keyboard/trackpad/screen)
I noticed while booting the new kernel that it starts out at a reasonable brightness, but at some point, around a second in, it switches to the lower brightness level.  My wild guess is that the kernel starts out with a compiled-in reasonable default, and then at some point in the bootup, it reads a config file from the filesystem and changes the brightness based on that.  (The downside to solid state storage is that this all scrolls by too fast for me to read what is printed when it changes the brightness).

I'm also wondering if this change affects intel-based laptops as well, or if it is limited to Arm64 laptops.  Or just the pinebook pro?
i have replied a few times to this issue over the last few weeks. see danielt's thread. i solved this by:

login to a tty
brightnessctl s 100%
"brightnessctl" is not installed on either of the installs on my PBP.  Guess it's not part of the default install.

However, it's easy enough to find as the package is called "brightnessctl" (at least in Debian).
yes i use brightness-udev, brightnessctl and light on mainline kernel with good results.

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