How could Fediverse group search be different from Fediverse hashtag search?
You should be able to use the ! operator to specify groups (example: !fediversenews). Thereafter a keyword to specify content.
Example: !fediversenews misskey
Ideally, that should pull up all mentions of Misskey within @
Fediverse News.
Of course, that's not happening yet -- but I'd like it to happen.