You make it so that any activitypub feed from or to your instance injects ads - actively work to put an MitM in the system so that any time your instance ingests a federated post, you drop in an ad into the thread. Then, E^3 - embrace it by getting your people to develop whichever software, extend it with advertising-friendly features, and extinguish by making it inoperable without phoning home to your ad server.