This sounds good, but what about discoverability?

There should probably be a way to merge project lists on various forges into a potentially huge index that can be browsed and searched, independently of each particular forge. Maybe it already exists?

Federating software projects so they can be interacted with from any forge frontend is the main focus. But federating the search engines internal to each forge is another important aspect. When federated search becomes a reality, looking for a project B on forge A will give an answer even when it is hosted on forge B.

Nowadays, with over 90% of the search run by Google, it does not matter much. Discoverability is whatever Google decides it is. But this is not desirable and more importantly it should not considered to be a solution to the discoverability problem. On the contrary dominance of Google is the main problem of discoverability and the only way to solve it is to provide sound alternatives.

imho the fediverse will have to come to be much more than social media type exchange of messages via activitypub. federated search is a major additional pillar that is currently largely absent (and is technically very different)

Well, there's sepia search for Peertube, possibly something like that could be built into a forge server software one day. I don't believe it is in the ForgeFed spec though and IMO it doesn't belong there.