Per the release notes our only supported UPnP server with Mosaic 1.0.x is MinimServer and this is the server software that we use as an internal engineering reference. It’s free and available for MacOS, Windows, Linux, most popular NAS platforms, and Melco.
There are many UPnP server software packages out there and they all interpret the UPnP “standard” differently. It would be impossible for us to support various quirks of all of these options so we elected to focus on the one option that is the most stable and follows the UPnP standards the closest.
We’ve had good luck with almost every other server with the exception of Asset. It has some odd behaviors which cause some issues in certain setups.
There’s more information in the FAQ (which is also part of the distributor documentation that we sent out at release time):