On Kindle 7’s outdated WebKit, both feed loading and article opening failed because the code relied on Set and DOM properties(too modern) that were missing, causing “undefined is not an object/function” errors. I could fix it by adding defensive null/type checks across DOM and helper functions, and implementing a full Set polyfill (has, add, delete, clear, forEach) to ensure compatibility without changing the existing logic. Now that I'm checking, the Hacker News articles don't correctly load. Only shows the URL.