Site feed only shows activity in one site

We have "Joined Sites" and "Following" so we know what the user is interested in, but we don't have any way for the user to casually browse whats new in all of their sites.

Create a global feed page that sources content from all following and subscribed.

It should use an algorithm to filter out redundant content, or unimportant content.

The feed page is opened with a button in the top right next to the notifications button