I may be missing something obvious, but can you search for main url of a post? Trying avoid posting duplicate content. The search doesn't seem to check the url field for local or all search options.
I'm not sure of any programs that will do this for you but Lemmy has a pretty nice API that you can use and there are libraries you can use for languages like JavaScript: https://github.com/LemmyNet/lemmy-js-client
import { LemmyHttp } from 'lemmy-js-client
const client = new LemmyHttp( 'https://beehaw.org/' )
const response = await client.search( {
listing_type: 'Local',
q: 'https://www.huckmag.com/article/sex-workers-and-the-kink-community-are-fighting-back-against-instagram-deplatforming',
sort: 'TopNineMonths',
type_: 'Url'
} )
console.log( response.posts.length ) // Should print '1' to the console
Edit: This can also be done without the library, got me interested and I've been playing with it.
This is essentially what the library does when you don't need authentication: