I would strongly expect that every client localizes by itself, because otherwise each player would have the same language in game. That would not make much sense. I would expect only the unique key of the localized string is replicated, and there is some efficient lookup mechanism for actual licalization.
When a FText is sent from the server to the client, do the client receive the FText already localized from the server, or do the client localizes the FText itself?
If it’s localised text then it will be handled on the client side. Culture invariant text will be sent as-is though.
Thank you for your answer. To be sure, I just have tried with 2 differents instance of Unreal Engine each of them having different cultures and it looks like replicated texts are handled correctly client-side.