It's astounding how much every single system out there fights and fights and fights against showing you your directories, as they are.
I started but didn't finish a Rygel + local-search (nee Tracker) plugin to try to finally get that. I wish the upnp media services were better. I keep telling myself I'll build a nice client/controller... Some day.
What're the chances VLC will do what you want as both server and client?
It's one tickbox away in Jellyfin: Libraries > Display > Display a folder view to show plain media folders