It annoyed me that there was no RSS feed for the UK Government petitions website at https://petition.parliament.uk. I decided to fix that.
You should be able to access the RSS feed at https://rss.dinwoodie.org/petitions.rss. Just point your preferred RSS feed reader to that address and it should work everything else out for you. Don't have an RSS feed reader? Try putting "RSS client" into your favourite search engine.
This was a quick hack; I've aimed for "good enough", not "good".
Every hour, a GitHub Action runs, which fetches the first page of a
JSON-formatted list of most recently published petitions, as published at
https://petition.parliament.uk/petitions.json?page=1&state=recent. This is
reformatted into RSS XML using jq, which GitHub Actions then publishes as a
static file.