In our next major update (likely to be released sometime next week), we'll be removing support for the "activity stream" as both a destination page and widget.
We're making this change because the Activity Stream is one of the most underused features in the platform, yet it happens to be one of the most complicated ones to maintain, since nearly every action ties into it in some way. In our research of active Crowdstacks, many had disabled the feature entirely.
We are still supporting the Content Stream, which is a subset of the Activity Stream, for v1 sites. Thus, if you are using an activity stream widget, it will become a Content Stream once the change is made. The difference is that the Content Stream only focuses on new posts, while the Activity Stream is a log of posts and all actions, which can be quite overwhelming.
This also means that, for automation rules, the "add to activity stream" action will no longer be supported (and will be removed from any existing automation rules you have in place).
While some Crowdstacks were using the Activity Stream, its overall usage across all of our customers was very low. By removing it as a feature, we are making our code base much less complex, which should allow for faster development of new features in the future.