Brightness on Lenovo not working in Pop!_OS

On my old laptop, a Lenove IdeaPad identified as Intel Core i7-3632QM processor, Intel Ivybridge Mobile graphics by Pop!_OS, the brightness is not set. Although the Fn key (F11 and F12) are working shown by on screen display with brightness icon, but the is not taking effect. Stuck on whatever brightness level it is.

After searching and tried some solutions, the one that worked is from Ask Ubuntu/769006:

1. open terminal
2. open /etc/default/grub , eg. using micro:
   sudo micro /etc/default/grub
3. append acpi_backlight=vendor  to the GRUB_CMDLINE_LINUX_DEFAULT  line, to become:
   GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"
4. save and close editor
5. update grub and wait until it is back to prompt:
   sudo update-grub
6. restart

It works in my laptop, if it does not work for you, then try another solution. Since Pop!_OS is based on Ubuntu check also solutions for Ubuntu.