I installed dotnet45 via protontricks --gui cli cmd. Note, this is the first game I've ever had not work out of the box on steam play. So, protontricks/winetricks was new to me, but I watched a Chris Titus Tech Tips video on protontricks on youtube and that gave me the info I needed to install dotnet45. Note, that during the error message lots of error messages and seeming restarts of the dotnet45 install process occur. But be persistent and keep hitting next/ok, it will eventually install. Once installed the game runs fine. Maybe a bit laggy but that might just be because my FPS is low due to running all settings on high. Still playable with my low end graphics card.