You should know that UE4 features built-in support for integrating a number of features of the Steam platform into your Windows and macOS games. 

Are you developing a game using Unreal Engine 4? You should know that UE4 features built-in support for integrating a number of features of the Steam platform into your Windows and macOS games. 

Networking and online features are said to be handled through “the Steam Online Subsystem plugin. When it’s enabled for your game, you will have access to the following Steam features through UE4’s unified Online Subsystem API.”

Here are the features here:

• Online sessions and invites.
• Matchmaking via peer-to-peer lobbies or dedicated servers
• Firewall/NAT negotiation for peer-to-peer multiplayer via Steam Networking
• Player authentication – new in 4.20
• Rich presence – new in 4.19
• Voice chat
• Friends lists
• Stats and leaderboards
• Achievements

What is more, UE4 is said to support additional Steam features outside of the online subsystem:

• Steam Audio
• Steam VR
• Steam Controllers

The team has recently made progress with adding new features and improvements including rich presence support in 4.19 and player authentication support in 4.20. They’ve also enhanced their Steam leaderboard implementation to be more consistent with online subsystems for other platforms. 

You can learn more here.