Mobile Multiplayer

Does UE4 allow mobile multiplayer? If so, do you have a tutorial?

There no difference between how mobile or desktop multiplayer operates in UE4 so use any multiplayer tutorial, keep in mind internet is internet and TCP/IP is TCP/IP and it works the same on all devices. Only difference in OnlineSubsystems avable to use which is normal if you use diffrent system then Windows and fact that you need to consider fact that user may use either wifi and mobile network that can suddenly disconnect and in case of mobile network bandwidth usage is the thing

If you making turn based game you might consider using HTTP as that protocol is more friendly for that and should be better for bandwidth limits, but that requires to code own server and code C++ on UE4 (or else you try to use VaRest)