First here is the official website https://docs.tandoor.dev/ . Basically it is a cookbook combined with a grocery list, and a meal manager. I personally only use the cookbook and grocery list. A very nice feature is that i can add all the ingredients of a recipe to the shopping list instead of having to do it manually.
I never used Plex but jellyfin works great for me. I can really recommend it but I do not have a big library.