Thanks for the info, didn't know that about Plex. A couple of a hours does not work with my workflow. I get a movie, add it to my media folder, and then I want to watch it, so I'm not surprised I missed it.
You can have the library update on change or at set time intervals if the auto detect doesn’t work.
as i said in my ancestor post i'm far from a power user. its quite likely i tweaked some setting several years ago and forgot about it. I put something in my flex drive and it's there within seconds.
I believe config settings exist for Plex to be more aggressive. Alternatively if you use third party software like Radarr or Sonarr they can use webhooks to update instantly when media is added
You can change the frequency to be as short as you want, fyi.
Jellyfin syncs on changes if the media location is local, their regular sync is only there as fallback for network shares.
plex also syncs on FS change (It's never failed for me) but that might be an OS/FS dependent thing. Works great on ZFS + Linux for me.