I found AudioRelay by stumbling around wanting to stream audio from a pretty basic mono Ulefone rugged phone to a slightly more sophisticated Blackview rugged tablet (four decent Harman Kardon speakers).
Thus far I can stream from my Musicolet library and this is great. The only thing that is missing is a way to control the tablet volume from the phone, for the simple reason that the tablet is usually on the other side of the room. I’ve tried doing it through KDE Connect but it’s not completely stable.
Thanks for a great product! I look forward to seeing it develop further. And if you have some suggestions for getting KDE Connect to work I’m all ears.