https://www.gamespot.com/articles/two-years-after-launch-rainbow-six-siege-hits-a-ne/1100-6457230/

Rainbow Six Siege has set a new concurrent player record on PC, and that's immensely impressive given that the team-based shooter launched more than two years ago. Following the launch of Siege's new Operation Chimera update, the game hit a new all-time high for concurrent players: 176,856, according to Steam's own public player data.

SteamCharts data shows that Siege has grown substantially over the past few months. For comparison, the game's previous peak concurrent record was around 125,000 players in February this year, so the game has added around 50,000 concurrent players in a month. As PCGamer points out, this data only comes from Steam, not Ubisoft's Uplay service.