Plex does not recognize them in terms of pulling down metadata but you can still organize them in folders and browse that way. I find the Plex route is a healthier way to engage with video content than platforms that just keep serving you whatever the algorithm thinks will keep you peeled to the screen. It's more intentional and less of a passive consumption kinda thing.

tl;dr: Yes, but probably takes some effort for most content.

Plex will play the files, but metadata is hit or miss. If it's something that's on thetvdb or themoviedb, it can be matched as a series or movie, respectively. With some effort, you could also probably include all the relevant metadata when downloading the videos, then have plex use local metadata, which could cover anything not big enough for the big metadata providers.

I think it's also possible to find plug-ins/scripts that will pull metadata directly from youtube, but I've had bad luck relying on that stuff and then development stopping, so I avoid it these days.

but won't it be hassle to follow that?