I have made plenty of projects that has some Multiplayer integration, these are all made using Unreal Engine. Currently working on a VR multiplayer game. I have some experience with replication and networking in Unreal Engine.
Dimentional Dead uses connection to Steam to add a player to your survival Match, you must work as a team to survive the waves of zombies and discover every easter egg there is.
Freddy's Kart is a multiplayer racing game, you can play with your friends inviting them via Steam. The game has a lot of powerups and a lot of fun.
I've made multiple other multiplayer tests, like a simple multiplayer shooter and a For Honor like game.