When you use the search in Liftoff, it takes you to pick an instance that you're searching from. It should hypothetically be a search through all the posts that insurance knows about, meaning everything on the insurance and all instances it is federated with.
In-browser, I know that Lemmy.world allows you to search among your instance's communities or among all (known, federated) communities. It would be nice if that were an in-app option.