http://u.qdnx.org/file/rozzin-20170203T211751-atltava.html
#GNUsocial has supported both #ActivityStreams JSON and #AtomPub w/ AS XML extensions in the client API for years now; for example: https://loadaverage.org/api/statuses/home_timeline/andstatus.as https://loadaverage.org/api/statuses/home_timeline/andstatus.atom