[Arnavion]

Doesn't seem to work for any of the ~50 URLs I tried with. Eg:

https://www.youtube.com/feeds/videos.xml?channel_id=UCS0N5ba...

... works but:

https://www.youtube.com/feeds/videos.xml?channel_id=UULFS0N5...

... is 404.

I'm guessing it's only a feature of playlist URLs which that SO answer is about, not RSS feed URLs.

[crtasm]

Sorry, my notes were lacking. Change UC to UULF and use it with this URL to get the Videos feed for a channel:

https://www.youtube.com/feeds/videos.xml?playlist_id=UULFS0N...