Debian: Brightness control does not work

I have just installed Debian on my Acer Aspire laptop; it has a Ryzen 5 CPU and a Radeon Vega AMD card. All is going pretty much fine, only problem is **I can't change the screen brightness!** I have tried with the dedicated buttons on the keyboard, I have tried from the bar in the settings menu, nothing; the slider moves but the brightness of the screen remains unchanged. This is driving me crazy.. I have also tried going into /etc/default/grub and changed the GRUB_CMDLINE_LINUX_DEFAULT value, but still no progress. Here is my grub file: I have read online that adding acpi_backlight=video should fix the problem, however it didn't for me... What is going on? How can I fix my brightness? I want to be able to use the brightness slider or the keyboard buttons to change it! -------------------------- **EDIT:** Wanting desperately to take control over my screen's brightness I have just tried using xbacklight but it also does nothing!! I installed it, set a new brightness percentage, and it simply does nothing! What is going on? Nothing seems to work..