This Unreal Engine 4 (C++ & Blueprints) project contains a complete example of various multiplayer topics:

• Spawning various actors,
• interacting with objects in the environment and showcasing them online
• Online connection through Steam

Written tutorials for each project can be found on the following links:

Co-op online puzzle game prototype in Unreal 4.22 - Part 1

https://medium.com/@bluebubblebee/how-to-create-a-co-op-online-puzzle-game-in-unreal-4-22-b7ce3fdb94d

Co-op online puzzle game prototype in Unreal 4.22 - Part 2

https://medium.com/swlh/co-op-online-game-prototype-in-unreal-4-22-e890a3b8892c

Co-op online puzzle game prototype in Unreal 4.22 - Part 3 - Connecting interactive actors in different rooms across the network

https://medium.com/@bluebubblebee/connecting-interactive-actors-in-different-rooms-across-network-in-ue-4-22-c255095231b3

Co-op online puzzle game prototype in Unreal 4.22: Multicast events - Part 4

https://medium.com/@bluebubblebee/multicast-events-in-ue4-22-b8a5688d9465

How to Connect a Multiplayer Game with Steam

https://medium.com/swlh/ue4-tutorial-how-to-connect-a-multiplayer-game-with-steam-ccc89bd8d8a9

Unreal Engine Version: Unreal 4.22