What directory to use for 'Sync with Installed Epic Games'?

Pretty much the title. I've tried the launcher directory and the directory with my game installs, and both times it's said 'Sync complete', but none of the games have shown up in the library. Where am I supposed to be syncing from?

The drive is NTFS and I'm on Linux if that makes a difference, but given I can successfully import games manually I don't think that affects it.