That would be Kodi which I now use on a Mini-PC with Lubunto which has replaced my TV Box and my Media Player (plus that Mini-PC also replaces a bunch of other things and even added some new things).
Before I went down a rabbit whole of trying to replace my really old Asus Media Player (which was so old that its remote was broken and I replaced it with my own custom electronics + software solution so that I could remote control that Media Player from an Android app I made running on my tablet) which eventually ended up with Kodi on a Linux Mini-PC also replacing my TV box, I had no idea Kodi even existed and was just using the old Media Player to browse directories with video files in a remote share (hosted on a hacked NAS on my router, a functionality which is now on that Mini-PC which even supports a newer and much faster SMB protocol) using a file browser user interface to play those files.
It was quite the leap from that early 00s file browser interface to chose files to play on TV to a modern “media library” interface covering all sorts of media including live TV (why it ended up also replacing my TV box).