The whole reason I host plex is that I want an offline experience that I curate myself. The requirement for internet to authenticate and shoveling crapware in my face pushed me towards trying Jellyfin. The Jellyfin UI on TV and mobile is not as flashy and polished as Plex, but it is extremely functional and respects users choices.

Been a happy Jellyfin customer for years now though I only use it to organize and browse my library now. Actual playback is either MPV on PC or Kodi over NFS on TV. After trying many many players, these were the two I found best for respective platforms, nothing else even comes close.