Enabling vkBasalt with Steam Proton 5.13:

 1. From a Linux terminal:

    # Note: The paths to libvkbasalt.so on your machine
    #       might be different from what is written here

    cd $HOME/.steam/steam/ubuntu12_32
    ln -s /usr/lib/libvkbasalt.so

    cd $HOME/.steam/steam/ubuntu12_64
    ln -s /usr/lib64/libvkbasalt.so

    mv steam_vkBasalt_i386.json $HOME/.local/share/vulkan/implicit_layer.d
    mv steam_vkBasalt_x86_64.json $HOME/.local/share/vulkan/implicit_layer.d

 2. From within Steam client:

    Set game's launch options to: ENABLE_VKBASALT=1 %command%

 3. Lauch the game and verify that vkBasalt is actually
    working by toggling it on/off with the Home key.
    If it isn't working then try to replace the relative paths
    to libvkbasalt.so in the two JSON files with absolute paths.