A little confused about DLNA

[TheDreadPirate]

DLNA is just a generic protocol for streaming media. Jellyfin goes the extra step of making some attempt to ensure that devices can play the media well. If it doesn't have a profile for your device, it uses a conservative generic profile and converts to very compatible codecs. You can create custom DLNA profiles that specify what your device can handle and then Jellyfin will send the files, unmodified, when the file fits within that custom DLNA profile.

uPnP is not related to DLNA. It is a protocol for clients to create port forwarding rules automatically. Port forwarding is only needed for apps that need to be accessible on the Internet. Since DLNA is LAN only, period, there is no relationship between DLNA and uPnP.