Forgefed creates an extension to the ActivityStreams format. I don't know how Mastodon, Lemmy, KBin and others will handle those. However, they will be able to

Forgefed creates an extension to the ActivityStreams format. I don't know how Mastodon, Lemmy, KBin and others will handle those. However, they will be able to handle the vanilla parts. So perhaps, they can participate in notifications and discussions/reviews.