Maybe not exactly what you’re asking for but this is what we did to accomplish this:
*Create a custom server host platform, running on a server with a listen URL of some kind attached to a static port.
*The client will make a network connection to request a new server session to the host platform.
*The server host platform will spin up an instance of an Unreal game server in its own process and return the connection details (port information).
*The client will then connect directly to the game server (or through the host if you want to do some fancy tunneling).
I’m not aware of any unreal-specific way to start up instances of a server aside from just doing the work on my end. This is somewhat similar to a matchmaking server but we use the access pattern for spawning up specific instances for players to connect to.
I hope that helps somewhat