Based on the replies when Firaxis announced it was "retiring services" for the multiplayer and challenge modes in XCOM 2, it seems like a lot of players didn't realize XCOM 2 even has multiplayer. It does! Or at least it does until March 28, when an update will remove it from the Steam version on PC. Guess we'll have to get the achievements before then.
"The decision to retire these services isn't something done lightly," Firaxis wrote, "but it does allow us to refocus our resources. We appreciate your support and thank you for your understanding."
While competitive multiplayer in the XCOM games was never seen as its main attraction, it was enjoyed by those who dove into it. Here's a showdown between two of PC Gamer's staff in XCOM: Enemy Unknown from all the way back in 2012. There were even multiplayer mods, like one that added co-op to XCOM 2. It's a shame to lose the multiplayer, though presumably whatever resources were tied up in keeping it online will be diverted into Firaxis's current project, Marvel's Midnight Suns.
This update will only affect the Windows version of XCOM 2 on Steam, with multiplayer in the Mac, Linux, and console versions remaining online.