Well, the "remote control" function can be partially realized by KDE connect, and we can stream other device's media content by Audiorelay. 😂 Although those ways are not as satisfactory as the solutions via BT, it's better than nothing.

I'm using KDE Connect from cellphone to partially "remote control" zx707, just like controlling any other android devices, under the same network. It can do pausing, resuming, adjusting the volume, skipping to the next track, and switching between already opened apps. Maybe it's not exactly what...