Auto-brightness service is broken. Possible attempt to fix was to built it from source rather than the using Sony blobs. It fixed notification light though.

adb shell dumpsys sensorservice > als.log
adb shell dumpsys display > display.log

However, no valuable information has been generated. With vendor blobs, sigprof said:

Apparently illumination_service has a bug it calls accept() without initializing the length pointed to by the 3rd parameter, and due to some uninitialized garbage there the call fails with EINVAL. I tried to make a binary patch to pass something acceptable to the syscall, and it seems to work, but obviously patching proprietary binaries is not a solution.