I reached out to the maintainer of Newsblur, and they told me there was nothing they could do, and that I should reach out to Pinboard's maintainer, who never answered.

Long story short, I finally got to fixing the problem myself. And I did it really dirtily, which I'm actually proud of because I usually want to do everything "the right way".

I'm fixing the feed with RegEx matching, publish the result to GitHub pages and subscribe to that instead.

Anyway, I'm posting it here because, although niche, perhaps it can be useful to someone else.

Accompanying post on dev.to: https://dev.to/jeromegamez/after-more-then-20-years-i-publis...