Samsung BDF7500 Plex app does not show 4digit code

It’s due to Plex’s move to TLS 1.2, which older Samsung devices don’t support. You might be able to get around it by setting up a proxy: Plex app (orca 2.012) showing user offline - #11 by dane22

Otherwise, your only option would be connecting to a server that doesn’t require authentication on your local network.