rssify

Since everyone is pitching their own, I built https://github.com/fran-penedo/rssify, which started as a fork of https://github.com/h43z/rssify. The basic functionality is similar to Vinnl's: give it a URL and some selectors and it builds the RSS feed. From this, I added a few things: templates (if you want to subscribe to individual projects within a webpage, like fanfics in ao3), transforms (when the data is not quite the text of the DOM element), a flask server you can use to add new URLs you have a template for and update the feeds, and a userscript to add the current URL using the server.

This python script https://github.com/h43z/rssify serves me well to get and RSS feed for websites that don't provide one.

Yes I have. Here you go https://github.com/h43z/rssify