I have not tested the audio transmitter type adapters (audio class device), which do not support 'multimedia' controls (play/pause, volume etc.). For some reason a phone can manage a fairly reasonable connection to the headphones, much greater distance or obstacle immunity than any dongle can do.
It has become clear to me that at least on Windows, the A2DP Bluetooth technology for headphones is not doing very well.
I have now tested numerous USB Bluetooth dongles in order to find a reasonable, working dongle to be used with WH-1000XM4 with Windows 10.
