Having access to ActivityPub sources could help gather posts from all types from within the fediverse.

The most common activitypub servers are of mastodon. Which would allow to get all those communities some brew goodness. But it doesn't stop there. Integrating with activitypub means that any source that uses activitypub standard could grant to get more than just toots on mastodon. You can get blogs seamless from writefreely like, pixelfed instagram like posts, and many others as listed on fedidb: https://fedidb.org/software