Try Nova f-droid.org/en/packages/org.courville.nova/ It scan your videos for movies and series and then it downloads the poster, background art, information of the serie/movie and information of each episode, you can also download subtitles.

There’s also kodi f-droid.org/en/packages/org.xbmc.kodi which I think is a more complete option, but it was designed for TVs and not for phones. I also think the fdroid version is generally outdated.