I apologize if this is old news, but I just noticed it. It looks like Kagi has added Fediverse Forums as a default Web search option.
I think brave (*search) let's you do the same thing with their goggles feature which let's users make custom search filters. I could be mistaken though
(and yes I know Brave as a company comes with baggage. Pretty much all of the search options do unfortunately :/)
Edit: I'm taking specifically about Brave search. I cant see any reason I'd ever want to use Brave browser frankly.