I have the slowdown issue with this game that require vsync to be disabled which is done by modifying the config file
This is supposed to be where the config file is: https://pcgamingwiki.com/wiki/Momodora:_Reverie_Under_the_Moonlight#Configuration_file.28s.29_location
Here is where the game files are on my computer
/home/me/.steam/steam/steamapps/common/Momodora RUtM/
I see no config.ini anywhere