I got so fed up with Plex constantly shoving their streaming service and nagging me to log into Plex servers when I just want to stream my own files locally that I threw my hands up and installed Jellyfin[0]. It's severely lacking in the same polish and functionality as Plex, but I'm pleased that I can run Jellyfin without ads or having to create a non-local account.
[0] https://github.com/jellyfin/jellyfin