Status update. @xrav3nz developed this Discourse Wellfed plugin that I have been testing in the past two weeks.
https://github.com/xrav3nz/discourse-wellfed
Importing RSS feeds from different sources and into different categories works very well! You can define the frequency, and in theory you can add dozens of feeds without hogging your server.
The only point pending is assigning the topics created to the right user. In fact, this seems to be a problem in Discourse and not in this plugin. The topics created via RSS poll are assigned to the correct username. However, it happens often that topics will be created first by the regular JS Embed workflow, scrapping the HTML content and assigning the topics to the default username.
This plugin updates the content of these newly created topics as soon as the RSS process pulls them for the first time. Content rendered through RSS feed is much more reliable than HTML scrapping, so the automatic re-rendering is very convenient. The plugin should be able to reassign these topics to the right username, but (if I understood this well) it cannot because of a bug in Discourse.
@xrav3nz has submitted a patch that should fix this problem:
https://github.com/discourse/discourse/pull/5771
We will report back if/when this problem is solved.
If you are looking for this multiple RSS feeds feature and you don’t mind (much) about different usernames applied to different RSS feeds, this plugin is ready for your use.