Gregory's Server
Sure, Meta's not going to buy anything. But do you know what happened to local shops in the 80s and 90s when Wal-Mart opened a store in their town? They died.
Not because Wal-Mart bought them out, but because WM's economies of scale lets it run on razor thin profit margins, and can outcompete local ships on prices. And once WM established dominance, they then raised prices to increase their profits.
Make no mistake, a similar situation will happen if FaceBook creates an ActivityPub instance.