Comment by tonyedgecombe

It worked in NetNewsWire, a macOS feedreader.

RSS is a bit of a pain as most feed readers will accept malformed XML (unlike Atom feeds). Hence you end up with a lot of malformed XML.

Having said that it mostly looks valid:

https://validator.w3.org/feed/check.cgi?url=https%3A%2F%2Fst...