Had to get latest https://github.com/z0z0z/mf-install via wayback machine as repo is deleted

Steve Fox's report was most helpful. If you've tried running the game before, switch to desktop mode and delete the compatdata folder. Then force Proton 5.0-10 and run again to recreate the folder. Quit the game via the steam overlay. Download the mf-install script from the wayback machine's archive of https://github.com/z0z0z/mf-install and extract (I used the latest master). Open the desktop mode terminal, cd to the extracted mf-install location and run WINEPREFIX=/home/deck/.local/share/Steam/steamapps/compatdata/64320/pfx PROTON=/home/deck/.local/share/Steam/steamapps/common/Proton\ 5.0 ./mf-install.sh -proton