Do you know about Embed Discourse comments on another website via Javascript?
But if you think that multiple topics link to a page then you might be able to use the TopicLink table to do a search of topics that link that URL (probably with the Data Explorer plugin) and then you’d have the topic and post IDs so you could link to them.
I don’t think there’s an endpoint to get them. A plugin could make one available, I think. Also, Discourse GitHub doess something sort-of similar, so that might help.