In this particular case I am using gerbera, successor to mediatomb, but have noticed with other servers.

Select UPNP/DLNA server->Audio->Album [for example]

For large libraries, I have to wait more than a minute while foobar2000 sits there and network activity spins. True for Android and iOS.

8player [on iOS] and BubbleUPnP are both considerably faster - just a few seconds until I can view list of Albums [or Artists, etc]

I disabled album art on server as an experiment, but it did not substantially help.

Folder [ie "PC Directory"] view works just fine