It looks like the link you shared is working now.
The links I have configured in my rss2email application are all showing HTTP 200 OK, with suitable content too.
False alarm?
YouTube Channel pages still have the application/rss+xml meta tag so it's possible that this is a temporary outage somehow but it seems unlikely. I think they just silently killed RSS on YouTube.
The RSS URL you pasted is now working.
It looks like the link you shared is working now.
The links I have configured in my rss2email application are all showing HTTP 200 OK, with suitable content too.
False alarm?