MOBA game style Multiplayer Network System

Dear Unreal Community,

I’m working on a mobile MOBA game now and having some difficulties. I watched the Unreal Engine tutorial on Multiplayer Blueprint that they use Steam Online Subsystem to be able to host game and let clients join game. I searched on some website and would like to ask, do i need a dedicated server for this? as i saw the tutorial video they just plug in those online subsystem then be able to create sessions on Steam and joined by clients. I read the online subsystem documentation that i can use facebook, google play etc… is it true?

And on all MOBA game, normally it’s a match making process like Paragon, League Of Legends, once client click join/play/matchmaking, then clients start to search for match. Well… i don’t need a real match making now, i just need a system that clients click join and they’ll join with other 5 players (3v3)? all 6 are clients, how does server able to create a session automatically? or should i ask how normally MOBA works? is it one of the player will create a session and other clients to join? but the player who create session is client as well? Please advise how can i do this MOBA style multiplayer… thank you very much!!!