Radarr

Radarr is a movie collection manager for Usenet and BitTorrent users. It can monitor multiple RSS feeds for new movies and will interface with clients and indexers to grab, sort, and rename them. It can also be configured to automatically upgrade the quality of existing files in the library when a better quality format becomes available.

Major Features Include:

Adding new movies with lots of information, such as trailers, ratings, etc.
Support for major platforms: Windows, Linux, macOS, Raspberry Pi, etc.
Can watch for better quality of the movies you have and do an automatic upgrade. eg. from DVD to Blu-Ray
Automatic failed download handling will try another release if one fails
Manual search so you can pick any release or to see why a release was not downloaded automatically
Full integration with SABnzbd and NZBGet
Automatically searching for releases as well as RSS Sync
Automatically importing downloaded movies
Recognizing Special Editions, Director's Cut, etc.
Identifying releases with hardcoded subs
QBittorrent, Deluge, rTorrent, Transmission, uTorrent, and other download clients are supported
Full integration with Kodi, Plex (notification, library update)
A beautiful UI
Importing Metadata such as trailers or subtitles
Adding metadata such as posters and information for Kodi and others to use
Advanced customization for profiles, such that Radarr will always download the copy you want