@maffeis #ActivityPub is for federation whereas #micropub and #microsub are for interacting with your instance, so they are not really exclusive though.
Micropub is already supported by tools like micro.blog, @ia Writer and such.
Not sure if anyone has implemented it on top of an ActivityPub backend though.
#Webmention, #WebSub and #Microformats would be the more direct #IndieWeb “competitor” to ActivityPub, but eg @snarfed.org and @pfefferle are both showing that the two can be bridged