A vérifier
Visit the channel’s main page.
Right-click anywhere and select View page source.
Search for data-channel-external-id and look for the value that immediately comes next. In my case, it’s UCfXdejDvNviqilmJ9DvGuow (don’t include the quotes).
Tack that value onto the end of this URL
https://www.youtube.com/feeds/videos.xml?channel_id=
Submit the new URL to your RSS reader.