It's because of an unsupported middleware called Vivox. It doesn't seem like there is any workaround for now.
Here's an issue about it to track progress - https://github.com/ValveSoftware/Proton/issues/5531
Another way of setting your GPU profile is to use Corectrl.
To get access to hidden features, it is recommended to add amdgpu.ppfeaturemask=0xffffffff
to your /etc/default/grub
and after that, run:
sudo update-grub
or
sudo grub-mkconfig -o /boot/grub/grub.cfg
Details here.
I found that in my system I was getting double images and flickering, whenever I turned my head (almost like the cable on my headset was broken). To fix that I had to add this to my /home/USER/.local/share/Steam/config/steamvr.vrsettings
file. Shutdown SteamVR and Steam, before you edit this file:
{ "steamvr" : { "enableLinuxVulkanAsync" : false, } }
Pay attention to the formatting of that file. There is a comma after each line, except if it is the last entry in that code block.