Actually I think they’re using their own plugin and/or forked version of Discourse. Pretty cool customization! Note that the pieces in the news stream on the front page are not topics. They have created their own route /news/{id}, with it’s own type of object, a ‘News’ object.
You can achieve a similar ‘media stream’ effect with Topic List Previews. However, note that Topic Previews are for topics. Also, if you want an sidebar like that you’ll need to override a template.
You won’t be able to achieve the exact Elektronauts experience without some relatively substantive work on a new plugin. Or you could ask them to take a peek at their code 