They have a tag in the main page to point to it but browsers don’t really surface that anymore I guess?
There's a Firefox addon to fix that. It's called RSSPreview, but besides providing previews it also adds a little button to the address bar on sites that have tags like that so you can find the feeds in the first place.
Is that why I haven't had any problems? I thought it was either Google A/B testing again or my ad blocker updating often enough to keep up, but I do have a user-agent changer installed in Firefox that's configured to tell YouTube I'm on Chrome...