In general most micropub clients authenticate using an IndieAuth mechanism which micro.blog also supports and this allows apps (Newsblur in this case) to send formatted data (an article’s title, URL, and a person’s reply, for example) to be published on third party websites. Developers interested in the pieces might inquire in the IndieWeb chat about the quickest and easiest method for implementing or to see some other examples and find open sourced clients/servers that already do most of the heavy lifting: https://chat.indieweb.org/dev. It would be great to see Newsblur added to the growing list of clients that can publish to independent third party websites.
Unless and until Newsblur were to support this, I notice that it does have IFTTT support, so one might be able to carefully write some recipes that allows some functionality to dovetail with any website that has a micropub endpoint. I’ve documented some similar work I did using IFTTT to get the Inoreader feed reader to post reads, bookmarks, and replies to others’ sites to my WordPress website using micropub. I would abandon Inoreader for a reader with good Micropub support.
h/t to Jeremy Cherfas’for bringing this to my attention.