Ubisoft has been the only party pooper so far with EGS' freebies (Rayman Legends and For Honor). The rest have been capable to be run without a client, even with a handful needing -EpicPortal comandline argument (or others) to force a launch.

Thanks for letting us know, do you know if the Steam version has the same requirement?

According to the game page on Steam, yes: "Requires 3rd-Party Account: Uplay (Supports Linking to Steam Account)".

So this is another game that needs a crack even If you have bought it properly.
I can't see any mention of Uplay on the game page either.