https://support.plex.tv/articles/200392126-using-the-library...
> The Folders option is available for all media types, and lets you browse the media folder structure directly based on the folder hierarchy on disk. Browse By Folder is a sticky setting, letting you use Grid, List, or Summary view to browse your drive’s directory structure.
I've accidentally put TV shows in the movies category and had them not show like you describe.
If you have say "movie.mp4" then make two copies of a jpeg named "movie.jpg" and "movie-fanart.jpg" alongside the movie file. Plex will then show this.
You could generate the jpeg using ImageMagick or similar from a base image (per show say) and with text overlay.
I have some scripts that does this and it's better than nothing.
At least my movies are reasonably well-catalogued. My TV shows are still a mess because of how inflexible their naming policy is.
Ugly though, if you ask me ;)
and auto-metadata from IMDB and other API is bad if you have niche videos (me: documentaires for anarchism, feminism, anti-colonialism). so bad it can replace good data with bad data (example sub.media/c/trouble documentary series becomes "good trouble" series)