Hi Samuel_Crow welcome to the forum
I’m not clear about exactly what you have in mind to do, but most Discourse pages can be output as RSS (maybe not exactly what you had in mind as XML, but it is a subset) or JSON.
For example
https://meta.discourse.org/t/is-it-possible-to-write-a-custom-client-other-than-a-web-browser/51671.rss
https://meta.discourse.org/t/is-it-possible-to-write-a-custom-client-other-than-a-web-browser/51671.json