Yes, I think Plex was an XBMC fork and Kodi is the new name of XBMC. Jellyfin forked from Emby, I think when it became closed source. I never used Emby. Plex always seemed to cost money in confusing ways and that turned me off. My initial TV just used NFS shares on a unix machine and a Netgear NeoTV box (~2009) but eventually the codec support was too poor so I moved to XBMC on the Shield and then a number of years later to Jellyfin server on Linux with Jellyfin client on the Shield.