interactions are not really stored in the system in any standard way. because of that, there’s not a single method to find these.
in the best case, an interaction is stored as a taxon on an appropriate observation field. in that situation, you can query for observation field values (ex. https://forum.inaturalist.org/t/searching-for-food-plants-of-parrots/17506/2)
additionally, there are some other ways to get information stored this way: https://forum.inaturalist.org/t/add-interactions-to-species-pages/433/2/
some people also capture this information using other kinds of observation fields, tags, projects, observation notes/description, and though duplicate observations tied to the same photo, etc. each of those kinds those kinds of cases requires a different way to get the interaction data. it’s not pretty.