You’ll need the vulkan-mesa-layers to be installed, as well as lib32-vulkan-mesa-layers for 32 bit applications. Check if these are installed. And DRI_PRIME=1 should be entered as a command in the launch options of the game, which would require %command% to be subsequently. So, DRI_PRIME=1 %command% should be the complete launch option for the steam game.
Alternatively you and try DRI_PRIME=1! %command% as a lanch option which should enforce the dGPU to be used instead of the iGPU, if I’m not mistaken.
Did you even have green artifacts on your Laptops build-in screen? eDP is the embedded display port the internal display is connected to. If not didn’t saw any green artifacts on it, you won’t need to do that or the following stuff, which I’ll describe anyway.
Kernel parameters could be added to the kernel cmdline via the dracut drop-in file.
sudo nano /etc/dracut.conf.d/cmdline.conf
The file may not exist, create it and add the following contents
# etc/dracut.conf.d/cmdline.conf
kernel_cmdline+=" amdgpu.dcdebugmask=0x200 "
Keep the spaces in the front at the end, as dracut would complain about it otherwise.
I’m not certain if it is strictly required, but I usually run sudo dracut-rebuild when I’m adding kernel parameters for good measure.