WiiM Sound as default as WiiM Ultra default audio output

[Tunguska2]

I have a ultra streamer and two WiiM sound as a stereo pair for the ultra. I already created a group including the ultra and the two sounds.
My issue is, that every time i listen to a song, streamed, to the ultra, it won‘t recognize the group and starts playing without any sound.

going to app, I can chose the Ultra+Sound group but then next issue appears and each sounds is playing a stereo signal and not the dedicated left/right signal, i assigned to them.

I wish I could have an option for the sounds as the default audio output, pretty much like bluetooth, optical or line out.