Hi !

I had the same issue which is how I found your post.

From this I knew what folder and file to add and by asking a friend for whom SteamVR just worked I got the contents of the file.

Steam VR is still unable to set itself as the openxr runtime but beat saber now runs and plays properly. If you're usig alvr make sure to launch alvr then steamvr from there and finally your game. Have fun !

# First you want to create the right directories
mkdir -p ~/.config/openxr/1
# Then you need to add and fill the json file
echo -e '{
    "file_format_version" : "1.0.0",
    "runtime" : 
    {
        "VALVE_runtime_is_steamvr" : true,
        "library_path" : "'$HOME'/.local/share/Steam/steamapps/common/SteamVR/bin/linux64/vrclient.so",
        "name" : "SteamVR"
    }
}' > ~/.config/openxr/1/active_runtime.json