Like PlutoTV, Curiosity Stream, and YouTube. 3rd party repositories, such as the SlyGuy Repository, contain more plugins like Disney+, Paramount+, Hulu, and Netflix.
It supports Blu-ray Discs, CDs, DVDs, USB Flash Drives, local Hard Disk Drives, AirPlay, network file shares, basically every video, audio, and image format available, subtitle files, and even retro game console ROMs.
Pause, skip, and rewind live TV shows.
Completely automatic commercial detection/skipping, with manual correction via an intuitive cutlist editor.
Intelligently schedules recordings to avoid conflicts.
Parental controls to keep your kids out of the good shows.
There is a seemingly endless supply of knowledgeable MythTV fans in the various interest groups that are ready to share their thoughts on any problems you might encounter.
Metadata for media files will automatically be updated by using media databases. This provides posters, movie trailers, descriptions, information about actors, etc.
Player and server are available to a huge number of platforms, including AppleTV and Amazon Fire TV as well as many NAS servers. It's pretty hard to find a NAS or STB that doesn't support Plex.
Active and lively support forums where the developers and other users engage to quickly resolve any issues you may experience, which will be few and far between anyway.
Add the Premiere option for around $5.00 per month and you get a full featured DVR that will play and record Live OTA TV, IPTV, Cable or Satellite signal and a great EPG (Electronic Program Guide)