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The TFS marketplace features the Activity Feed extension, available at https://marketplace.visualstudio.com/items?itemName=davesmits.VSTSActivityFeed. This free extension, created by Dave Smits, brings in the capability of viewing what's happening in your team project at a glance in one place. The extension is available as a dashboard widget, as well as a subpage in the work hub. Activity Feed gives a summary of all recent changes in work items, commits, pull requests, and builds. It tells who changed a task, who logged a bug, and who committed code. The extension supports configuration, so you can decide to filter out what's not relevant or simply configure which backlogs the work updates should be published from:

The team rooms functionality has been completely removed in TFS 2018 https://blogs.msdn.microsoft.com/devops/2017/01/04/deprecation-of-the-team-rooms-in-team-services-and-tfs/. However, the introduction of social experiences built around you, including the search, follow, and comment features in work items and the activity feed extension, provides a far more engaging solution.