First, check to ensure your systems up to date. Open a terminal and type
$ sudo pacman -Syu
This command will update all packages on your system, including graphics drivers if there are any updates available.
Garuda Linux uses the KDE Plasma desktop environment by default, so you can adjust brightness settings through the desktop environment's settings.
Go to System Settings > Display and Monitor > Brightness & Gamma. From there, try adjusting the brightness settings and see if the flickering persists. You might also want to experiment with different power management settings to see if it makes any difference.
If the issue persists after trying these steps, it could be related to the graphics drivers or compatibility with your specific hardware. In that case, you might want to reach out to the Garuda Linux community forums or the AMD Radeon Linux support forums for further assistance. Don't forget to provide details about your system configuration when asking for help, such as the exact model of your AMD Radeon R5 graphics card and any relevant error messages you encounter.
You may also consider tweaking the compositor options within the KDE Display Settings options under compositor.
