Hi, it seems the .appimage Linux version is not working. Here is the error message when I try to run it (Linux Mint) : 

/tmp/.mount_OneShoSb7Z1i/usr/bin/oneshot: symbol lookup error: /lib/x86_64-linux-gnu/libgio-2.0.so.0: undefined symbol: g_module_open_full

here seems to be the issue but I'm not very good at Linux :  https://github.com/AppImage/AppImageKit/issues/1162

Would it be possible to solve it ? Thanks ! 

Try downloading the Windows version and adding it to Steam as a non-steam game! Then you right click it and enter properties, compatibility and press the "Force to use Steam compatibility tool" thingy!