Just look at first post!This seems to be described here.
And obviously, you need to define a FFS sync stored as a *.ffs_batch file, not as a *.ffs_gui file. Plerry, 17 Feb 2019, 12:14
BuTbka, 08 Feb 2019, 23:21"/home/iam/FreeFileSync/Bin/FreeFileSync_x86_64" "/home/iam/SyncSettings.ffs_batch"