@autogestion A month or two ago I visited the https://test.activitypub.rocks site and at last found out, which exactly features are REQUIRED for a client app to formally declare its support of #ActivityPub.
I've added "Client discovers the URL of a user's outbox from their profile" already, working on other features. What's most important is that internal data model of #AndStatus is already compatible with #ActivityPub, I hope :-)
The only hard part to implement is compatible OAUTH (AndStatus supports two variants of OAuth, but it looks like I will need the third for ActivityPub...)
After completion of the REQUIRED features I will create the new "ActivityPub" Social Network Type (in addition to the three existing) and will start actual testing...
Unfortunately, I don't see any working _real_ (not a toy) server with Client to Server layer support, where I could register as a user and test my client app ;-(
?!