Plex is an enterprise solution, if you need your tech illiterate grandma to access the media it's easier to pay them. If it's just a local network or you're okay with going down a rabbit hole of setup, then Jellyfin does everything and does it better IMO (Plex requires you to be online to login before it shows you your local data, plus you're sharing information on what media files you have to Plex).

I personally have been using Jellyfin for years, and my only complain is that the LG app is slow and I get some videos that stuck for a few seconds in it (probably some codec thing, that I could fix by transcoding the media but I haven't been bothered enough to figure it out)