Cannot change brightness on Acer laptop

[myangelmegu]

I use Acer Aspire 4750G. Specs are Intel Core i7-2630QM with it’s integrated GPU and NVIDIA GT 540M that’s disabled from BIOS.
I can change the brightness slider but it won’t do anything.
“ls /sys/class/backlight/” gives: “acpi_video0” as output

The only change I have done is disabling acer_wmi using "sudo tee /etc/modprobe.d/blacklist-acer-wmi.conf <<< “blacklist acer_wmi”
acer_wmi will keep my Wireless LAN Hard blocked and won’t let me use wifi. Hardware key doesn’t help either. So I’m forced to disable it, which allows hardware key to work as usual and enable wifi and bluetooth.
I am not sure if losing brightness the side effect of it. I tried removing /etc/modprobe.d/blacklist-acer-wmi.conf, reboot and then doing a “sudo modprobe acer_wmi”. But that didn’t fix the brightness, but introduced the wifi and bluetooth issue again. I didnt do a “ls /sys/class/backlight/” after this tho.

Please can anyone help me regain brightness control? I’m happy to provide as much information as needed.

Other info: hostnamectl:

Static hostname: aspire4750g
Icon name: computer-laptop
Chassis: laptop
Machine ID: 67be83149ff94649b3db8c39d1bb24e6
Boot ID: 32051462f7b742e78179408bd5a51d8e
Operating System: EndeavourOS
Kernel: Linux 6.14.5-arch1-1
Architecture: x86-64
Hardware Vendor: Acer
Hardware Model: Aspire 4750
Firmware Version: V2.15
Firmware Date: Mon 2011-12-05
Firmware Age: 13y 5month 2d

[eso]

Welcome to the forum @myangelmegu,
Add to
sudo nano /etc/default/grub

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"

and
sudo grub-mkconfig -o /boot/grub/grub.cfg

[myangelmegu]

Thanks for the response.
I opted to install EndeavourOS using systemctl-boot so how would I apply this fix for my case?

[eso]

@myangelmegu ,
https://forum.endeavouros.com/t/what-is-the-equivalent-of-grub-cmdline-linux-default-for-systemd-boot/41877
Use google and optionally deepl.com btw.

[myangelmegu]

SOLVED - for people using systemctl-boot:
sudo nano /etc/kernel/cmdline
Add this line at the end
acpi_backlight=video acpi_osi=Linux
then do
sudo reinstall-kernels

For grub just add the line acpi_backlight=video acpi_osi=Linux to GRUB_CMDLINE_LINUX_DEFAULT

acpi_backlight=vendor would just make my brightness to max and remove any option to change brightness. “acpi_backlight=video acpi_osi=Linux” worked flawlessly.