Kodi - Kodi is an award winning free and open source media player that got its start on the Xbox console.
Universal Media Server - Universal Media Server allows you to host your entire library of video, music, and pictures, and broadcast them conveniently to a wide variety of different devices.
Android TV - Android TV is a version of Android made for TV's
PseudoTV - PseudoTV Live is channel-surfing for your media center.
Veso - Veso is an open source media server. An emby/jellyfin fork that will move to a js react framework and focus on remote/rclone mounted media rather than local storage.
OSMC - OSMC is a free and open source media center built for the people, by the people.