I can’t seem to figure out how to set a player to a spectator. I know I can create a spectator actor and possess it using the player controller, but I am using multiplayer and I can’t figure out how to do it using gamemode, gamestate, etc.
The server should spawn the spectator pawn serverside from within gamemode. gamemode already has the variable/property set which class to use, so take that and feed it into spawnActorFromClass. after the actor is spawned, put your client playerController into the possess node to control the new pawn. where are your problems? what have you tried? maybe i dont get it 
when do you want this to happen (begin play, on death, …)?