Thanks for the input. I tried setting up RSS locally, but Liferea decided to use this generic commit feed URL: https://github.com/discourse/discourse/commits/master.atom. I tried adding the GET parameters from the Web page URL, but that didn’t filter the results. The feed only shows the most recent 20 items, so none of the recent security alerts were shown.
I took a look at the links you provided, however they appear to require non-free JavaScript to sign up to them, so I’ll keep my eyes open for alternatives.