Hi thanks for the report. This feed is working on planet where the blog is subscribed, but indeed looks like it's not valid. It will soon be replaced by new one once moved to the new blog (https://www.goffi.org/u/goffi) I'll check validity at this moment (in the coming weeks I guess).
Error on the Goffi blog's RSS (atom) feedcreated
The feed at https://goffi.org/blog/goffi/atom.xml seems to be malformed ; apparently it has the right doctype but somehow it's rendered as plain HTML... Weird, wget gets a "XML 1.0 document, UTF-8 Unicode text, with very long lines" but the w3c validator can't parse it: https://validator.w3.org/feed/check.cgi?url=https://goffi.org/blog/goffi/atom.xml