It looks like any GitHub feeds, eg. https://newsblur.com/site/646785/recent-commits-to-newsblurmaster, get reported as misbehaving with the reason “Feed has no original page. (404)” but it has a link to the original page (see https://i.imgur.com/otLe4P0.jpg) and the link seems to work.
Is this a bug with newsblur or is there really something wrong with the feed?