>>1456072i use Taiga
https://taiga.moe/however it doesn't automatically scan everything on your disk. you first add anime to the list and then it will scan your media folders for episodes, and you can click something in the menu to automatically play the next unviewed episode.
it will also recognize if you're playing an anime that's not on your list and you can click a button to add it.
however it does still sync with one of several online anime list websites
for a purely offline option you can look at Jellyfin
https://jellyfin.org/, which is aimed not just at organizing media but also at streaming it in your home so you can watch it on your phone & shit. basically a non proprietary version of Plex.
or Shoko Desktop
https://shokoanime.com/ (what I used to use before I decided it was too complicated and moved to Taiga)
