A: macOS and Linux typically use native USB audio class drivers. You generally do not need a special driver for these operating systems. This guide is for Windows only.
The BR21 is installed as a COM port, not a Bluetooth adapter. Fix: Re-run the installer and select "Bluetooth Radio" mode, not "Serial Bridge" mode. Some generic drivers default to serial debugging. jieli br21 driver link
Knowing the hardware brand can help narrow down the exact firmware version needed. A: macOS and Linux typically use native USB
The plug-and-play nature of standard USB Audio Class devices means Jieli BR21-based receivers often work seamlessly on Linux and macOS as well. jieli br21 driver link