This is neat, definitely works for finding feeds on more busy / obscured / ad-covered sites, such as news.
I see that main part of the code is in JS anyway. Perhaps a fully-local bookmarklet would work even better, without having to rely on a site, CloudFlare, etc, etc.
That's an interesting idea! I'm definitely not a frontend expert, so I'm not sure if it's possible to implement a UI within a bookmarklet. It would also have to be pretty big code-wise to cover all the fallbacks and edge cases. Maybe a hybrid would be an extension that runs things locally, but with the switch I did from hcaptcha to Cloudflare Turnstile the friction seems to be almost gone.
Thought I would share this in case someone may find it useful. :) Feel free to drop any feedback if you run into issues, RSS as a whole can be fractured to work with since sites have so many configurations, but if there's something obvious I missed please let me know.