Hi, Marcin here – creator of JPLAY. I saw your support email as well.
You're not doing anything wrong. The Innuos Stream1 does not support UPnP as a renderer (audio endpoint) – it only functions as a UPnP server. That's why JPLAY lists it as a library but not as an audio output.
This is confirmed by Innuos themselves: https://innuos.com/kb/innuos-upnp-streamers/
The other devices you mentioned (Aurender, Gato, BlueSound) do advertise themselves as UPnP renderers, which is why JPLAY picks them up as audio outputs without any issues.
Unfortunately, this is a limitation on the Innuos side and not something we can work around in the app. You may want to reach out to Innuos and let them know you'd like UPnP renderer support – the more users request it, the more likely they are to consider it.
Marcin

