Just the button: https://github.com/aureliendavid/rsspreview

XBrowserSync and Floccus don’t sync to local files, unless you self-host the server or a webDAV respectively.

Lofloccus makes it easy to spawn a local webDAV server (making Floccus save your bookmarks to local files) which I can then sync with rsync or Syncthing or whatever system I already like. It’s only available for Windows and MacOS though.