Just install MediaMonkey for Android and browse the files using the UPnP node.
Then click the cast icon in the right corner and select "Onkyo receiver".

Does it work this way?

It's up to the App to provide the display, MediaMonkey only provides metadata and browsing structure.

Yes I access music on PC with an android app supplied by Onkyo (I use their TX-8150 receiver) and choose as my DNLA server "MediaMonkey" which is running on PC. So I use MMW as my DNLA server. Problem is that the interface the app supplies is very basic - there is no search function and I can not see metadata on song or albums. I think that interface is provided by MMW in part because the interface provided by say Logitech Media server on the app is slightly different (even worse). So I am trying to understand how to improve this.

MMA can only do Chromecast at the moment, not send to a DLNA client. (MMW can do this). You may want to check out BubbleUPnP.

I have a music collection on windows 10 PC and play it on my Onkyo receiver via DNLA. Mediamonkey runs on PC and the android app provided by Okyo lets me select Media monkey and then browse A-Z various categories (such as artist or title) and play them.

I would like a better GUI so I can see album covers, search for songs etc. I hoped that mediamonkey for android would provide this but although it plays songs on my PC on my smartphone via PNP it does not play them on the receiver. The PNP interface is just what I need - but I want it to go to my receiver. Or maybe there is some other way I am missing.