Hi there, welcome to the forum.
When you are in the grub line that you want to use (e.g. boot with free drivers), press button E, go to the end of the line starting with linux and add amdgpu.dc=0 at the end (with a space before...), then CTRL+x
This is to try booting the live iso. Then, if it works (you can boot and install) but you are not be able to boot the installed system, you can try it also there. If it helps, this can be easily set as permanent with the Garuda Boot Options tool in the Kernel parameters field.
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