Note that as the character ':' is reserved in NTFS, Proton cannot create its wineprefix in the NTFS steamapps/compatdata directory. To solve this, you need to s

Note that as the character ':' is reserved in NTFS, Proton cannot create its wineprefix in the NTFS steamapps/compatdata directory. To solve this, you need to symlink that folder to a filesystem that support filename with the character ':', such as ext4. More info here: https://github.com/ValveSoftware/Proton/wiki/Using-a-NTFS-disk-with-Linux-and-Windows https://github.com/ValveSoftware/Proton/wiki/Using-a-NTFS-di... https://github.com/ValveSoftware/Proton/issues/82#issuecomment-415099440 https://github.com/ValveSoftware/Proton/issues/82#issuecomme... Windows and Linux can share steamapps directory though, I've tried this by installing my games to an external SSD with NTFS filesystem and I can play the games under Proton on my PC and Windows at another PC. I'm not sure whether this will work for games that have native Linux version though