> And wouldn’t the Jellyfin metadata (or a workable subset) be available using its DLNA pluging?
Yes. The major inconvenience is remote access, as I can't add it to my mother's WiiM which is in a different city as where I host my Jellyfin server.
Also consider that sometimes the publicly exposed server can be in a different VLAN for security isolation from the day-to-day home network devices, which complicates the DLNA discovery.