My AMD CPU graphics were interfereing with my dedicated GPU. Browse local files ( where WW1.exe etc are located ) and added a dxvk.conf file containing the line:

dxgi.nvapiHack = False

Hints: In the WW1_dxgi.log file I was seeing "DXGI: NvAPI workaround enabled, reporting AMD GPU" Alternative solution: run steam via:

export DXVK_FILTER_DEVICE_NAME="NVIDIA"; steam

Where "NVIDIA" (or "3060ti" etc) is unique to a single card as found via command: vulkaninfo

Without my fix an invisible window would take over my desktop. I could switch away using alt-tab. Additional resources: https://github.com/doitsujin/dxvk/wiki/Driver-support