Two Unreal Engine plugins that often go together.

SteamBridge – Steamworks SDK
Use Steamworks from Blueprint, no C++. Achievements, friends, lobbies, matchmaking, leaderboards, inventory, Workshop — all as nodes.

Easy Aim State Blend
An animation node. Syncs the character's aiming pose with the camera FOV. Removes desync and jitter when entering and exiting ADS.

For shooters and multiplayer projects heading to Steam.