In Discourse forums the feed for most categories can be set up by clicking the category, copying the URL from the browser’s location bar, and appending “.rss”
If you are using Safari for feed reading, then merely click the location bar, add “.rss” to the URL, press Return and Safari will ask
(Depending on how the forum was configured, appending “.json” instead of “.rss” will grab a JSON feed – doesn’t seem to be the case in the case of this forum.)