Google searched worked really well for reddit if trying to find an answer to a technical question or the like. How well will this translate for Lemmy? I assume it would be a lot more difficult as the post could reside on any number of smaller instances.
Since all posts/comments are public, all you need is some kind of indexer to organize them and a list of all the instances. There are people working on it right now. But in the meantime you can just add
(intext:"modlog" & "instances" & "docs" & "code" & "join lemmy")to your search queries to search all Lemmy instances.