I am getting errors in the logs, notably "Error 193: 1% is not a valid Win32 application". However, it refuses to locate the avformat-55.dll file despite it being present in C:/Program Files (x86)/FFmpeg for Audacity. I have gotten this fork to run and it seems to be more or less functional (I am also experiencing the disabled plugin bug another user reported).
To confirm, FFmpeg was functional when I was using vanilla Audacity.