For Plex:

In YouTube download-material settings: Extra-> check "generate nfo files"

In plex, create a library called "YouTube" or whatever you'd like. Use scanner: "Plex Video Files Scanner" set agent to "Personal Media."

Plex will use the nfo files generated by ytdl for metadata.

I believe there is a dedicated YouTube series agent, but those can be finicky. This way, ytdl has already done all the metadata work.