One potential solution here would be to cache (server side) all the hubs, so the client can just retrieve them. I’m guessing that something fails during the existing hubs retrieval because my library is large (even though the hubs/collections aren’t that big).
This is also happening to me. I have enabled locations (hubs) on my server and I can see them for that user on the server, but not on the plex ap on my Shield 2019. It is not updating