I'm excited about the pageview_actor table but I wanted to point out a minor bug with how actor_signature_per_project_family is computed. For the mobile apps, the accept_language parameter is not actually stable and changes based on the language being viewed in the app (i.e. en if you look at English Wikipedia but fr if you switch to French, etc.). Because accept_language is used in the computation of the actor signature across projects, app users will actually end up with different actor_signature_per_project_family values when they switch languages. In my brief browsing, I haven't seen any indication that this would happen in mobile web or desktop.
This is the query you can use to verify this behavior (if you scroll, you generally find an example pretty quickly of someone who visited multiple languages):
SELECT x_analytics_map['wmfuuid'] AS wmfuuid, uri_host, actor_signature, actor_signature_per_project_family, accept_language FROM pageview_actor WHERE year = 2020 AND month = 7 AND day = 10 AND hour = 18 AND access_method = 'mobile app' AND x_analytics_map['wmfuuid'] IS NOT null ORDER BY wmfuuid LIMIT 1000;