ActivityPub C2S Client for Android that not only has basic implementation of the ActivityPub Client-to-Server spec, but which has internal data model close to the ActivityPub/ActivityStreams data model.
And yet AndStatus is an Open Source multiple accounts client for multiple social networks, including GNU social, Mastodon, Twitter and Pump.io. AndStatus can combine your feeds from all networks into one Timeline, and it allows you to read and post even when you are offline.
This category focuses on the ActivityPub Client-to-Server (C2S) implementation. Initial discussions and description of this implementation are here: https://github.com/andstatus/andstatus/issues/499
Another related discussion on Groups/Lists support with comparison of these notions in different Social Networks (from Client app point of view): https://github.com/andstatus/andstatus/issues/248