I use a file browser that also plays audio and video: Total Commander

It’s not on F-droid, but it’s possible to add its repository to F-droid.

There is Just (Video) Player ;) f-droid.org/packages/com.brouken.player/

NPlayer is really good in my experience. It works with the vast majority of files. It sometimes struggles, but anytime that happens VLC picks up the slack. It remembers where you left off in individual video files. It’s not on Fdroid, sorry about that, but there are Android and iOS versions.

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 I also think the fdroid version is generally outdated.