Why can't I increase my screen brightness in Debian 12 basic install on my old Packard Bell Easynote Laptop?

I'm trying to increase the brightness of my screen in order to see well what I'm doing (because the set brightness is so low thay I can't see anything if I have some light behind me). Before asking here I have investigated and found some possible ways that didn't work for me: I tried to increase the backlight of my laptop (since it's too dark) by using brightnessctl (which teorically worked but didn't actually change anything, since the brightness didn't change) or xbacklight (which didn't work because, as I have understood, it's for intel GPUs), so I tried to change it manually in /sys/class/backlight/[device]. I could find a device called **radeon_bl0** inside the mentioned path, and some subdirectories inside radeon_bl0 such as: actual_brightness, bl_power (set to 0), brightness, device, max_brightness (255), power, scale, subsystem, type and uevent. Seeing that, I tried to do it with echo 200 > /sys/class/backlight/radeon_bl0/brightness. Actually, it changed the number inside the file (the cat command showed the new value), but the actual (physical) backlight was the same. I don't know why does this happen, but I think it could be related to brightnessctl not working. Thanks for reading this, I hope someone can help me :) PD: My GPU is an AMD ATI Mobility Radeon 9550 EDIT: The laptop is a Packard Bell Easynote PB26M00704