I assume you could use the google “site” boolean to search within a specific instance.

For example, starting your search with:

site:lemmy.world

And then add a space plus your search terms to give something like:

site:lemmy.world how to search

That would limit the search to indexed results appearing in the lemmy.world domain.

I have no idea how often any given instance is indexed by google’s crawlers…

https://en.wikipedia.org/wiki/Radome