I also noticed the youtube rss feeds are returning 404s now as well.
They are still working for me. Example: www.youtube.com/feeds/videos.xml?channel_id=UC5rT…
EDIT: This is the command I use to convert YouTube channel URLs into RSS URLs:
curl --silent "https://www.youtube.com/@thecodyreeder" \ | grep -Po '"rssUrl"\s*:\s*"[^"]+"' \ | cut -d : -f 2- | tr -d \"