This open-source, cross-platform media player has existed since the days of XBMC on the first-gen Xbox console. One of the best media management software for a proper streaming setup is Kodi.
You can also get Kodi working on a Gen 3 Fire TV, Fire TV Cube, as well as all the existing lineup of Fire TV Editon Smart TVs and soundbars. This tutorial will help you install Kodi on FireStick.