Lists are great for integrating with your IMDB Watchlist and for following automated lists.
While lists can be filtered on Genre, Year(s) etc, which filters are available depends on the source (ex: IMDB vs TMDB) but is typically rather limited.

Let’s have a look at some projects that can help with populating Sonarr/Radarr in a manual or automated way.

Containers

Ombi

Ombi-app/Ombi : Want a Movie or TV Show on Plex/Emby/Jellyfin? Use Ombi!

Ombi was already mentioned in earlier articles as something that you’d give to your spouse so s/he can easily request or directly download stuff without having to know about the complexities of Sonarr/Radarr.

But Ombi can be great for yourself as well, it has an easy-to-use interface for discovering new things which you can then send directly to Radarr/Sonarr.

Checkout the live demo

Overseerr & Jellyseerr

sct/overseerr : Request management and media discovery tool for the Plex ecosystem

Fallenbagel/jellyseerr : Fork of overseerr for jellyfin support

Checkout the UI

Traktarr

You can add Trakt lists in Radarr/Sonarr, or you could take things a step further and use Traktarr.

l3uddz/traktarr : Script to add new series & movies to Sonarr/Radarr based on Trakt lists.

Note that this is JSON configuration, there is no UI!

Discord

kiranshila/Doplarr : An *arr request bot for Discord

Mobile

LunaSea

JagandeepBrar/LunaSea : Self-hosted software controller built using Flutter

A mobile app to easily check all your *Arrs? Yes please!

Radarr & Sonarr Companion

Download the Companion

Other Projects

faulander/P4S : Premieres for Sonarr - a small sonarr companion app to find all the new shows you’ve never known you’re interested in!

TheUltimateC0der/listrr : listrr.pro creates and maintains lists on trakt.tv completely automated based on your filters.

suchacomic/Mubi-radarr-list : Scrapes Mubi for movies and produces a StevenLu type list for radarr.

petio-team/petio : Petio Request, Discover, Review (for Plex)