You could either try this guide I made some time ago (by modifying the internet search) or use lemmy’s built-in search (Thunder app implements it very well in my opinion).

keywords have some rules
need to use the Booles
that’s the way I type it baby
I don’t want to scroll forever

(search fu up-grades)
(search fu up-grades)

• communities: https://lemmyverse.net/communities
• posts: search feature of your instance