This is a known kernel bug for AMD backlight.
Check if you really have "two backlight services", or (normally) only amdgpu_bl0
ls /sys/class/backlight/
Check what systemd finds out
systemctl status systemd-backlight@*
Even if there are two, mask acpi_video0, to test if your system hardware buttons (assuming a laptop, or a capable keyboard, or shortcuts) can control display backlight.
That’s why we call it a bug .
The brightness values of Linux “kernel” and AMD “GPU” are of different scale, so 255 and 65000 are for 100%, for each case (numbers are from memory and maybe a little different).
With the current workaround, you just use one scale (0-255).
Check your settings with
find /sys/class/backlight/amdgpu_bl0/*brightness -type f -printf %f -exec cat {} \;
I still got the error but my linux still boots up not like my earlier install where I get stuck so I had to reinstall garuda dr460nized again in hopes that this was because installing rog-core. But at least it still boots up and I'm really hoping this will be fixed soon.