Mattflix is a private media server, allowing you to watch all your favorite TV/Movies. It is a labor of love.
Jellyfin is a truly open source media server. It's more straightforward than Plex, but with less bells-and-whistles, and might have spotty device support.
This can be iffy. It works on my Vizio TV and my Android TV, but not sure it'll support every TV.
Plex is the gold standard of media servers. It supports every device and has lots of features, but they are getting "VC-ified", so it's not free and they'll try to sell you on their other services.