Small script to control brightness on laptop with Intel chipset running Ubuntu. Fn brightness keys and xbacklight stopped working, but this worked. Pass an int between 0 and 100 representing the percent brightness you want. Call without args to get current percentage.

bright.py

#!/usr/bin/env python3

import os
import sys
import subprocess
from pathlib import Path

if os.geteuid()!=0:
    args = ['sudo'] + sys.argv
    os.execlp('sudo',*args)

bpath = Path("/sys/class/backlight/intel_backlight/")

bmax = int((bpath/"max_brightness").read_text())
bcur = int((bpath/"brightness").read_text())

if len(sys.argv)<2:
    print(round(bcur/bmax*100))
    sys.exit(0)
else:
    perc = int(sys.argv[1])
    val = str(int(perc/100*bmax))
    cmd = "echo " + val + " > " + str(bpath/"brightness")
    print(subprocess.getoutput(cmd))
    sys.exit(0)